Drizzle a little olive oil in a frying pan and cook the onions, mushroom, and bell pepper until soft. Drain off any excess liquid.
Add the turkey breast mince and brown off. Add one teaspoon of the dried mixed herbs, and salt and pepper. Set to one side.
Whisk the eggs in a jug with the other teaspoon of dried mixed herbs, and salt and pepper. Set to one side.
Grease a casserole dish (approx 30cm/12" long) with oil spray or melted butter.
Lay the bread down buttered side up.
Spread the turkey mixture over the bread and sprinkle with one third of the cheese.
Pour over the whisked eggs.
Sprinkle with the remaining cheese.
Bake in a 200C/400F/Gas 6 oven for 20-30 minutes until cooked through and golden.
When cooked, you can serve immediately. Or if you are prepping this to eat later, allow to cool, then cut into slices. Cover and store in an airtight container in the fridge for up to 5 days.