Preheat your oven to 375°F (190°C).
Wipe the portobello caps with a damp cloth, remove stems and gills, brush with olive oil, and season with salt and pepper.
Heat olive oil in a large skillet over medium heat, add sausage, and cook until browned, about 5-7 minutes.
Push sausage to the side and scramble the eggs in the cleared space until just cooked, then mix with the sausage.
Stir in diced basil and chives, adjusting seasoning with salt and pepper to taste.
Spoon the sausage and egg mixture into each portobello cap, then top with shredded cheese.
Place stuffed mushrooms in a baking dish and bake for 20-25 minutes until mushrooms are tender and cheese is bubbly.
Let cool slightly before serving. Garnish with fresh herbs if desired.
