Roast the onions and potatoes in a pan with butter. Season with salt and pepper and cook until the potatoes are almost ready - approximately 10 minutes on an even heat.
Step 1
Whisk the eggs together with the milk, nutmeg, salt and pepper and pour the mix over the potatoes.
Step 2
Place the pan to the middle of the oven and cook. Baking time - 20 minutes at 200° on fan.
Step 3
Mix the asparagus, spring onions, balsamic vinegar and pepper well and spread it on the hot frittata.