Preheat your oven to 190°C (375°F). Gently wipe the mushroom caps with a damp cloth to clean, then carefully remove the stems and set them aside.
Finely chop the mushroom stems. Heat olive oil in a skillet over medium heat, then add the chopped stems and minced garlic. Sauté for about 3 minutes until fragrant and slightly browned.
In a mixing bowl, combine the sautéed stems and garlic with shredded cheddar and mozzarella cheeses, breadcrumbs, chopped parsley, and a squeeze of lemon juice. Season with salt and pepper to taste, mixing until the filling is cohesive but not too sticky.
Use a spoon to generously fill each mushroom cap with the cheese mixture, pressing down lightly to pack it in.
Place the stuffed mushrooms on a baking sheet lined with parchment paper, arranging them evenly spaced.
Bake in the preheated oven for about 20 minutes, until the tops are golden brown and bubbly, and the mushrooms are tender when pierced with a fork.
Once baked, remove the mushrooms from the oven and let them rest for 5 minutes. This helps the filling set and prevents spills when serving.
Serve the stuffed mushrooms hot, with the cheesy tops slightly crisp and the aroma filling the kitchen.