Preheat your oven to 180°C (356°F) and lightly grease your ovenproof dish or skillet with butter or non-stick spray.
Chop your vegetables into small, uniform pieces. If using peppers or spinach, sauté them in a pan with olive oil over medium heat until just tender and any excess moisture evaporates, about 3-5 minutes. Let them cool slightly.
In a mixing bowl, crack the eggs and whisk vigorously until the mixture is smooth and slightly frothy, about 30 seconds. Add the heavy cream, season with salt and pepper, and whisk again to combine.
Stir in the shredded cheese and chopped herbs into the egg mixture, folding gently to distribute evenly.
Add the sautéed vegetables into the egg and cheese mixture, mixing gently with a spatula until evenly combined.
Pour the mixture into your prepared dish, spreading it out evenly with a spatula. Smooth the surface for a neat appearance.
Place the dish in the oven and bake for 30-35 minutes, until the top is golden brown and the edges are slightly pull away from the dish.
Remove the quiche from the oven and let it rest for 5-10 minutes. It will puff slightly and then settle into a firm, sliceable texture.
Slice carefully with a sharp knife, revealing a fluffy, cheesy custard with vibrant vegetables inside. Serve warm or at room temperature and enjoy!
