Preheat oven to 180°
In a large pan over medium-high heat, sauté the onions, red peppers, and green peppers in 30ml olive oil until soft. Set aside.
Fry sausages in the same pan until golden brown.
Cook butternut, but not all the way through.
Grease an oven pan with butter.
Mix all the ingredients in the oven pan.
In a separate bowl, whisk the eggs and milk together, and pour over mixture in the oven pan.
Sprinkle cheese over the mixture.
Bake for 45 minutes and serve hot with a side salad.