Frittata made with leftover Brussels Sprouts

Ingredients

• 500g Brussels sprouts, shredded in a food processor or thinly sliced by hand
• 300g fresh Mushrooms, preferably a mix, coarsely chopped
• 3 tbsp olive oil
• Salt and freshly grounded black pepper
• 8 large eggs
• 150g gruyere, coarsely grated
• 100g cheddar, grated
• 1 tbsp unsalted butter
• ¼ cup shallot, finely chopped
• 1 tbsp fresh rosemary, finely chopped
• ¼ cup carrot, grated