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Stuffed Portabella Mushrooms – Toaster Oven Easy

There are times, especially in the summer, when I just don’t feel like turning on the oven.  Yet I also love main course dishes that include melted cheese on top.  My solution?  Learn to love my toaster oven.  Try these stuffed portabella mushrooms in yours on a day when you crave a healthy, light but filling dish. They are a great vegetarian main course, or a side for chicken or fish, served hot or at room temperature.  You can easily double the recipe for 4 caps and still use the toaster oven if it's big enough (or baken them in 2 batches.)

stuffed portabella mushrooms, easy baked mushroom recipe

A stuffed mushroom would make an elegant picnic dish too. And no eggs, so it can stay at room temperature for a few hours.

Stuffed Portabella mushroom caps – 2 servings. Total cost $9.20 (less than $5 per serving) 


ingredients to make stuffed mushrooms

There is no standard size for large portabella mushroom caps - when packaged there are usually 2 or 3 in a package.

  • 2 large portabella mushroom caps (large enough to stuff) 
  • 2 cloves garlic
  • ½ medium onion (about ⅓ cup)
  • 3 tablespoons olive oil
  • 6 ounces fresh baby spinach (smaller, more tender leaves than regular)
  • 2 tablespoons ricotta cheese (soft cheese, like cottage cheese but no water or lumps)
  • ½ cup tomatoes, chopped (about 6 cherry tomatoes or 8-10 grape tomatoes)
  • 1-2 tablespoons chopped basil
  • Salt & pepper to taste
  • ¼ cup bread crumbs (I prefer Panko, Japanese-style bread crumbs)
  • ¼ cup shredded or grated Parmesan cheese

Equipment (besides toaster oven with its own tray)  

equipment for making stuffed mushrooms, grapefruit spoon is handy

In the left corner, you can see my grapefruit spoon - a handy item for cleaning mushroom caps!

  • Cutting board
  • Knife
  • Small spoon 
  • Large spoon
  • Garlic press
  • Measuring cups
  • Measuring spoons
  • Medium-large pan
  • Cheese grater or shredder 


  • Using either cooking spray or olive or other cooking oil on a paper towel, lightly oil the toaster oven pan.  (You can line the pan with aluminum foil and oil that instead – it’s less messy because you throw away the foil and the span stays relatively clean.)
  • Clean the outside of the mushroom caps with a bit of water and dry them.  (Don’t overdo the water or soak them, as the mushrooms will hold the water and get soft.)  Cut off the stems and use a small spoon to gently scoop out the black gills. If you have a grapefruit spoon (with serrated edge) it works well, but a regular spoon will do it just fine.  Try not to gouge the mushroom out as you take out the black gills – this is more like surgery than building demolition.
stuffed mushrooms - cleaning mushroom.jpg
  • Cut the onion into small pieces by laying the half, flat side down on the cutting board, then making slivers by cutting from the side into the middle.  Once you have slivers, pile a few up with the long side parallel to you and cut them in as the picture below shows. Presto – you have small pieces.
stuffed mushrooms - cutting onion.jpg
  • Cut the cloves of garlic out of the garlic head, take off the “skin” and press the garlic cloves.  If you don’t have a garlic press, you can smash them or cut them into tiny pieces.  
stuffed mushrooms - garlic.jpg
  • Chop the basil into small pieces.
  • Pre-heat the toaster oven to 375 degrees. 
  • Pre-heat the pan with 2 tablespoons of the olive oil. Add the onion and garlic and cook under a medium heat until they are transparent – about 5 minutes.                                          
stuffed mushrooms - cooking onion  garlic.jpg
  • Add the spinach to the onion and garlic. Cook a few more minutes until the spinach has wilted. Turn off the burner. 
stuffed mushrooms - spinach raw with stems off - small size.jpg

I take stems off the some of the spinach leaves (see white ramekin at left.) But some call that obsessive.

stuffed mushrooms - adding spinach.jpg

No need to cook spinach first, or add water. It wilts down in a minute or two.

  • Add the ricotta cheese, tomatoes and basil, then mix to combine all the ingredients in the pan. Add salt and pepper to taste. 
stuffed mushrooms - adding ricotta  tomatoes to spinach.jpg
  • Put the mushroom caps on the oiled pan (or oiled foil on the pan.)  Stuff half the contents of the pan into each of the 2 mushrooms.  You can press it down a bit, but don't slam it too hard - let it mound up.
  • Shred or grate the Parmesan cheese. Resist the urge to buy pre-shredded cheese – it has much less taste than the freshly grated/shredded variety.  If you don’t believe me, buy it and smell it – not much there.  Then, grate or shred some from a wedge of cheese you buy whole – yum.  
  • Put the panko and most of the Parmesan cheese into the now-empty pan (to soak up the last bit of oil), toss them together, and divide between the mushrooms.  Put the remaining bit of Parmesan on the top of the mushrooms and sprinkle with the last tablespoon of oil.  (Putting a bit of Parmesan on the top with oil makes for a crustier top, which I like.)   
stuffed mushrooms - ready to bake.jpg
  • Bake for about 20 minutes, until the top is crusty and the filling looks hot inside. 
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