Go Back Email Link
–+ servings

Toaster Oven Caprese Stuffed Portobello Mushrooms with Balsamic Glaze

Juicy portobello mushroom caps loaded with fresh tomatoes, melty mozzarella, and fragrant basil, finished with a drizzle of sweet balsamic glaze — all ready in under 30 minutes in your toaster oven.
Print Recipe Pin Recipe
Prep Time 10 minutes
Cook Time 20 minutes
Servings: 4 servings
Ingredients Method Notes

Ingredients
  

Mushrooms
  • 4 large portobello mushroom caps stems and gills removed
  • 2 tablespoons olive oil divided
  • 2 cloves garlic minced
  • 1/2 teaspoon kosher salt
  • 1/4 teaspoon black pepper freshly ground
Caprese Filling
  • 2 medium Roma tomatoes thinly sliced into rounds
  • 6 ounces fresh mozzarella sliced into rounds
  • 1/4 cup fresh basil leaves plus more for garnish
  • 1/4 teaspoon red pepper flakes optional
  • 1/4 teaspoon dried oregano
Balsamic Glaze
  • 1/3 cup balsamic vinegar
  • 1 teaspoon honey

Method
 

Make the Balsamic Glaze
  1. In a small saucepan over medium heat on your stovetop, combine the balsamic vinegar and honey. Bring to a gentle simmer and cook, stirring occasionally, for 5–7 minutes until the mixture is reduced by half and coats the back of a spoon. Remove from heat and set aside — it will thicken further as it cools.
Prepare the Mushrooms
  1. Preheat your toaster oven to 400°F (200°C) on the bake setting. Line the toaster oven baking pan with aluminum foil and lightly grease it with a drizzle of olive oil.
  2. Use a damp paper towel to gently wipe the portobello caps clean. Remove the stems by snapping them off, then use a spoon to scrape out the dark gills from the underside of each cap. Removing the gills helps prevent the mushrooms from becoming too watery during cooking.
  3. In a small bowl, mix together 1 1/2 tablespoons of the olive oil, the minced garlic, salt, and black pepper. Brush this mixture all over both sides of each portobello cap, making sure to coat them well.
  4. Place the mushrooms gill-side down on the prepared pan and roast in the toaster oven for 8 minutes. This initial roasting helps release excess moisture so your filling stays deliciously melty — not soggy.
Fill and Bake
  1. Carefully flip the mushrooms so they are gill-side up. Pat the inside of each cap dry with a paper towel to absorb any released liquid.
  2. Drizzle the remaining 1/2 tablespoon of olive oil over the inside of each cap. Layer in the filling: start with 2–3 fresh basil leaves, then alternate overlapping slices of tomato and mozzarella in a shingled pattern. Sprinkle with dried oregano and red pepper flakes if using.
  3. Return the stuffed mushrooms to the toaster oven and bake at 400°F for an additional 10–12 minutes, until the mozzarella is fully melted, bubbly, and beginning to turn golden at the edges and the tomatoes are tender.
Finish and Serve
  1. Remove the mushrooms from the toaster oven and let them rest for 2 minutes. Transfer to serving plates, drizzle generously with the balsamic glaze, and top with fresh basil leaves. Serve immediately while the cheese is hot and melted.

Notes

**Removing the gills is key:** Portobello gills release a lot of dark liquid when cooked. Removing them keeps your filling bright and prevents a soggy result.
**Dry the mushrooms after pre-roasting:** Don't skip patting them dry before adding the filling — this one step makes a big difference in texture.
**Mozzarella options:** Fresh mozzarella gives the best melty, creamy result. If you only have low-moisture shredded mozzarella, it will still work and will brown more aggressively.
**Store-bought balsamic glaze:** If you're short on time, a store-bought balsamic glaze works perfectly here.
**Serving ideas:** Serve these alongside crusty bread, a simple green salad, or over a bed of arugula dressed with olive oil and lemon for a complete meal.
**Make it vegan:** Swap the mozzarella for a plant-based mozzarella alternative and replace the honey in the glaze with maple syrup.

Tried this recipe?

Let us know how it was!