Preheat your oven to 375°F and line a baking sheet with foil or parchment paper.

Clean mushrooms by washing gently in your hands with running water. Remove the stems and set aside for chopping. Place mushroom tops (hole side down) on a paper towel to dry. Pat tops gently with paper towel to quickly dry.

Clean stems by rinsing well with water and finely mince. You should end up with just about 2 cups chopped stems.

Measure out spinach by packing leaves into the measuring cup then chop on a cutting board. Chop artichoke hearts on cutting board as well.

Melt butter in a large pan or skillet over medium-high heat and add minced mushroom stems and garlic. Sauté for 2-3 minutes, or until softened and fragrant, and then add the chopped spinach and artichokes.

Once the spinach has wilted, add cream cheese, Italian seasoning, salt, pepper, and red pepper flakes and stir it all up until the cream cheese has melted.

Remove it from the heat and fold in your grated cheese.

Adjust spices as desired.

Spoon spinach mixture into each mushroom cap.

Sprinkle with panko breadcrumbs for an optional but tasty topping.

Bake at 375°F for about 15-20 minutes or until filling is hot and melty and the mushrooms are deliciously tender. Larger mushrooms may need to bake a bit longer so just check for doneness and you're good to go! Feel free to Broil for 1-2 minutes to get the tops nice and brown before removing the tray from the oven.