Gratinated Portobello Mushrooms are a particularly delicious and effortless dish. You can prepare them all year round in the oven, but as their best, they are when grilled in a charcoal grill in the summertime. This easy recipe is also your friend whenever you’ll need a trouble-free meal, or you’ll get surprise guests and want something easy and tasty to entertain them.
How to make these Gratinated Portobello Mushrooms
This recipe makes one large serving or two small servings. It works best as an appetizer, but it can also be an essential part of your grill party and served with other grilled food like vegetables and meats.
As this dish is very low in carbs, it suits well a strict keto, too.
You can also serve this dish to a bigger crowd. In that case, just multiply the ingredients accordingly. More ideas further down in this post.
So, let’s take a look at how to prepare this easy and tasty dish:
First, take two large portobello mushrooms.
Remove the stems and use them for other purposes (more about that later in this post).
Place the portobello caps into a baking dish or a griddle. Set aside.
Take a small bowl and add 2 oz (60 g) shredded Gruyère cheese…
…2 tablespoons mayonnaise…
…2 crushed garlic cloves…
…and 1-2 teaspoons finely chopped fresh rosemary.
Here we go.
…until well combined.
Divide the mixture into the mushroom caps.
Add some fresh rosemary on top for decoration.
Grill, or bake in a regular oven at 350 °F (175 °C) for about 30 minutes…
…or until the cheese is melted and golden brown.
Let set 10 minutes.
How I came up with this easy keto recipe
I got the idea for this recipe during my recent trip to Greece. In one restaurant — Anemoloos, to be exact — in Santorini, I was served delicious grilled portobello mushrooms:
Actually, the same photo I posted here on my blog a couple of weeks ago.
Those gratinated mushrooms had feta, Gruyère, sun-dried tomatoes, and garlic butter. As a decoration, there were a few sprigs of rosemary. Immediately when I tasted the dish, I knew I want to create my own version when back at home. This was one of those really simple but very tasty dishes that are super easy to make. And that’s what I’m all about!
After returning home, I was playing with the idea of grilled cheese-gratinated portobello mushrooms and my own version of the dish I was served in that Greek restaurant.
Since I’m not that big fan of feta (it’s simply too sharp for me), I thought Gruyère cheese alone would be perfect for the gratin. I totally love Gruyère and its salty and distinct flavor. In Greece, they also have a variety of Gruyère, it’s called graviéra, and I actually bought some graviéra cheese for home.
I also decided to leave out the sun-dried tomatoes that the restaurant recipe contained since they are on a carby side. On the other hand, I wanted to boost the flavor of rosemary in my variation and not leave just a walk-on part for this wonderful herb.
The concept of garlic butter in the restaurant recipe was fascinating, so I decided to add a couple of crushed garlic cloves and some softened butter — that would beautifully bind the gratin ingredients together.
I went to the nearest store to buy the ingredients, only to notice they didn’t have portobello mushrooms! Now what? Luckily, they had giant button mushrooms (which are basically the same thing, just the immature version of the same mushroom variety), so I was semi-happy with my finding. The rest of the ingredients were easy to find.
At home, I made a carefully calculated mixture of 2 oz (60 g) Gruyère cheese, 1 tablespoon (15 g) salted softened butter, 2 crushed garlic cloves, and 1 teaspoon finely chopped fresh rosemary. I filled two stemmed mushroom caps with the cheese mixture and — as I didn’t have a grill available — baked in the oven at 350 °F (175 °C) for 30 minutes.
The result tasted really delicious, but to be honest, the texture of the gratin part could have been a tad juicier. More melt-in-the-mouth. But how to get it juicier? I happily gave up my idea about garlic butter and decided to replace the butter with mayonnaise. I was sure mayonnaise would provide just the juicy and succulent texture I was after.
Moreover, I also wanted to double the amount of mayonnaise. So, instead of just 1 tablespoon, I opted for 2 tablespoons mayonnaise. That should be enough to provide richness but not make the dish too greasy.
I grabbed my camera and started taking photos and videos while doing my experiments. After shooting the photos and the videos and preparing the dish, I was ready to taste it (that first bite you can see in one of the photos earlier in this post).
Indeed, this version with mayonnaise was super succulent and tasty! I totally loved it and was extremely positively surprised by how well this simple dish had turned out. I dare say that this version was as good (maybe even better?) than the restaurant version. Of course, in the restaurant, the surroundings, atmosphere, and especially the company adds to the overall experience, so I have to say the whole experience was much more enjoyable in that Greek restaurant, but if you consider only the food, my creation had nothing to be ashamed of.
Here’s the recipe for you to enjoy:
- 2 large portobello mushrooms
- 2 oz = 60 g shredded Gruyère cheese
- 2 tablespoons mayonnaise (preferably homemade, olive oil based)
- 2 garlic cloves, crushed
- 1-2 teaspoons chopped fresh rosemary
- Preheat the oven to 350 °F (175 °C) or heat a charcoal grill.
- Remove the stems from the portobello mushrooms and use them for another purpose.
- Place the mushroom caps into a baking dish or a griddle.
- Mix the rest of the ingredients (cheese, mayonnaise, garlic, and rosemary) in a small bowl until well combined.
- Divide the mixture into the mushroom caps.
- Grill, or bake in the preheated oven for 30 minutes, until the cheese is golden brown.
- Let set 10 minutes and serve.
|Per serving if 2 servings in total
Tips for variations
The easiest way to give more variation to this dish is naturally to swap the rosemary to another herb. To be honest, I associate rosemary with spa. Always, when I smell fresh rosemary, it smells like a spa for me! I’ve got no idea where this association comes from. Don’t get me wrong, though, I love to eat rosemary as well.
Some authentic herbs for this dish are oregano and thyme. Parsley is too bland, so I suggest choosing a flavorful herb. Mint is also a delectable option if you happen to like it. Basil loses its flavor when cooked, so I don’t recommend adding basil to the gratin. However, you can add fresh chopped basil on top of the ready gratinated portobellos when serving.
If you cannot access Gruyère, other sharp cheese is also suitable for the gratin. For example, Swiss cheese or sharp Cheddar are good options. And, you can also replace part of the Gruyère with feta in case you like feta.
This recipe is also a perfect appetizer recipe and ideal for entertaining when you use small, stemmed button mushrooms and fill them instead of large portobello mushrooms.
And now, some ideas on how you can use the stems of the mushrooms: for the easiest way, chop the stems finely. Mix them with mayonnaise and enjoy as a spread on your keto bread or as a condiment with your keto main dish.
If you want to put a bit more effort into your preparations (and if you have a huge amount of stems), chop them finely, fry with chopped onion in butter until done. Now, you can add this mixture to your omelet, or make tasty compound butter by adding an ample amount of softened butter (and maybe some herbs) to this mixture. Roll in a parchment paper into a tight roll, close the edges, place in the fridge, and let set for a few hours. Once set, cut into servings. You can also freeze the compound butter. This compound butter recipe is actually from my Finnish keto cookbook Järkevä ketoruokavalio.
This week was busy with Ketokamu stuff. We had lots of meetings, and we were planning our future product line. I also created a 3-ingredient keto popsicle recipe for our social media followers using coconut milk, our Ketolla spread, and stevia powder.
Usually, Finns go to their summer houses (or summer cottages, as we prefer to call them) and celebrate their Midsummer there with friends and family, good food, sauna, and boating. I usually go to our summer house as well but now decided to stay in Tampere. My parents are in the summer house currently, and I didn’t want to bother them.
Finns do have their specialties when it comes to Midsummer food. Those who love to have their carbs, eat potatoes with dill and herring. Grilling is also popular, as is frying different types of sausages. And, as the Finnish Midsummer is nothing without a cake filled with fresh Finnish strawberries and whipped cream, I also made a keto version of this favorite — though my version has some bells and whistles, too, like freeze-dried strawberries, crushed hazelnut, and a delicious chocolate drizzle.
~~~ Happy Midsummer! ~~~