In a large pan, heat 1 TBSP of olive oil. Cook sausage breaking it into small pieces. Set aside.
In the same pan in the sausage drippings, sauté the onion until translucent. Add in peppers and mushrooms cooking another 5-7 minutes on medium high heat. Stir in garlic and cook another 1 minute.
Stir in the kale. Season with Italian herbs, salt and pepper. Mix with cooked sausage in a large bowl. Let cool for 5-10 minutes.
Beat the eggs well and pour into the cooled vegetable and sausage mixture. Fold in the cheese. Pour the entire mixture into a well buttered casserole dish. Cover with foil and place in the fridge for at least 8 hours or overnight.
Pre heat oven to 350 degrees. Remove casserole from the fridge and rest at room temperature 15-30 minutes prior to baking. This keeps the eggs from becoming tough.
Bake covered for 30 minutes. Remove foil and bake another 20-30 minutes until top is golden. Center should be set and not liquidy or runny.