Preheat the oven to 350 degrees F and line a rimmed baking sheet with parchment paper or silicone liner.
Gently clean the tops of the mushrooms to remove any dirt or debris. Remove the stems from the mushrooms.
In a 12-inch skillet, add olive oil and set over medium high heat.
When the oil is hot add the spinach and artichokes and saute for a few minutes to soften the spinach.
Lower the heat to medium-low and add the cream cheese, mayonnaise, sour cream, kosher salt, black pepper, and red pepper flakes. Gently cook until well combined, about 5-10 minutes, depending on how soft your cream cheese is.
Add 1/4 cup of the Parmesan cheese to the mixture and stir until combined.
Remove from heat, and using a spoon, fill each mushroom cavity with a generous amount of stuffing.
Place them on your baking dish, sprinkle the remaining Parmesan cheese on top and bake for 25 minutes or until the top of the cheese is golden brown.
Serve immediately.