Prep the mushrooms: Preheat your oven to 400°F (200°C). Wipe mushrooms clean with a damp paper towel. Gently twist out the stems and scoop a bit of the inner gills to make room for filling. Reserve the stems.

Par-bake the caps: Toss mushroom caps with olive oil, salt, and pepper. Arrange them cavity-side down on a parchment-lined baking sheet and bake for 8 minutes. This step helps reduce excess moisture.

Chop the stems: Finely mince the reserved mushroom stems. They’ll add earthy flavor to the filling without extra carbs.

Cook the sausage: In a skillet over medium heat, cook the breakfast sausage, breaking it apart with a spatula, until browned and cooked through, about 5–6 minutes. Drain any excess grease if needed.

Sauté aromatics: Add minced garlic, chopped mushroom stems, and a pinch of salt to the pan. Cook 2–3 minutes until tender and fragrant. If using bell pepper or spinach, add now and cook until softened.

Mix the egg base: In a bowl, whisk eggs, heavy cream, and a pinch of pepper. Stir in cream cheese until mostly smooth. It’s okay if a few small bits remain—they’ll melt in the oven.

Combine the filling: Remove the skillet from heat. Stir in the egg mixture, cooked sausage, half the shredded cheddar, and sliced green onions. The residual heat will slightly thicken the mixture.

Fill the caps: Flip the par-baked mushrooms cavity-side up. Spoon the filling into each cap, mounding it slightly. Sprinkle the remaining cheddar on top.

Bake until set: Return to the oven and bake 10–14 minutes, until the eggs are set and the tops are golden. If the tops need more color, broil for 1 minute, watching closely.

Finish and serve: Let rest for 3–4 minutes to set. Garnish with extra green onions or a pinch of smoked paprika. Serve warm.