Stuffed Mushrooms

This is an amazing appetizer/side dish. It would go great with a steak dinner and it would be equally awesome as a snack during a football game.

8 oz. package of baby portabella mushrooms (or regular white mushrooms if you prefer)
1 thick slice of cheddar (1 oz) or 1/4 cup grated cheddar cheese
1/4 cup roughly chopped blanched spinach (frozen is fine but I cooked my own)
1/4 cup panko breadcrumbs
1/2 cup mascarpone cheese (or cream cheese)
2 cloves garlic (not pictured)
1/4 cup finely diced onion
1/4 cup finely diced bell pepper (I used a yellow pepper)
1/2 teaspoon black pepper
1 tablespoon Sriracha sauce (or regular hot sauce if that's all you have)

Crispy exterior, salty and ooey gooey cheese, a kick of spice from the Sriracha - serious flavor. And you know, if you had a little bacon or pancetta, that would be awesome in this as well, just chop finely and cook it as the same time as the garlic, onion, peppers, and mushroom stems. The only downside of this addition is that it wouldn't be vegetarian-friendly anymore.