Preheat oven to 375°F (190°C). Lightly grease a large rimmed baking sheet or 9x13-inch ceramic baking dish with olive oil.

Wipe mushrooms clean with damp paper towels. Gently pop out stems and finely chop enough stems to measure 1/2 cup (discard remaining or save for broth).

In a large skillet over medium-high heat, add 1 tablespoon olive oil and the sausage. Cook, breaking apart with a wooden spoon, for 6 to 8 minutes until browned and cooked through. Transfer cooked sausage to a paper-towel-lined plate.

In the same skillet with remaining drippings over medium heat, add chopped mushroom stems, minced shallot, and garlic. Sauté for 3 to 4 minutes until softened and fragrant. Remove from heat.

In a medium mixing bowl, combine softened cream cheese, cooked sausage, sautéed mushroom mixture, 1/4 cup grated parmesan, parsley, thyme, red pepper flakes, salt, and pepper. Mix thoroughly until creamy and evenly combined.

Arrange mushroom caps hollow-side up in the prepared baking dish.

Generously mound 1 tablespoon of sausage cream cheese filling into each mushroom cap.

In a small bowl, toss panko breadcrumbs with melted butter and the remaining 1/4 cup grated parmesan. Sprinkle a generous pinch over each stuffed mushroom.

Bake for 20 to 22 minutes until mushroom caps are tender and juicy, and the panko topping is deeply golden and crisp.

Garnish with freshly chopped parsley and serve warm on a party platter!