Preheat your oven to 400°F and prepare a baking sheet by lining it with parchment paper. This will prevent the mushrooms from sticking and make cleanup easier.
In a medium-sized mixing bowl, thoroughly combine the panko breadcrumbs, grated pecorino cheese, chopped parsley, sun-dried tomatoes, pine nuts, minced garlic, and ¼ teaspoon of sea salt. Add several grinds of fresh black pepper to enhance the flavor.
Arrange the stemmed cremini mushrooms, with the cavity side facing up, on the prepared baking sheet. Lightly drizzle each mushroom with extra virgin olive oil and sprinkle with a bit of sea salt to season. Carefully spoon the prepared filling into each mushroom cavity, ensuring they are generously filled. Drizzle a bit more olive oil over the filled mushrooms for extra moisture and flavor.
Place the baking sheet in the preheated oven and bake for 18 to 22 minutes, or until the mushrooms are tender and the filling is golden brown and crisp.
Once baked, remove the mushrooms from the oven and garnish with additional chopped parsley for a fresh pop of color. If you like a bit of heat, sprinkle red pepper flakes on top. Adjust the seasoning with more salt, if needed, and serve warm.