Steam or microwave potatoes until just tender. Cut into quarters.
Heat oil in 20cm-base, non-stick frying pan over a medium heat. Add onion and cook for 4 minutes or until tender. Add asparagus and cook for 2 minutes. Stir in potatoes. Reduce heat to medium-low. Preheat grill on high.
Whisk eggs, milk, salt and pepper in large jug. Add feta. Pour over vegetables and cook for 10 minutes or until egg is set and golden. Stand for 5 minutes.
Bring a saucepan of water to the boil. Add snow peas and cook for 1 minute. Rinse under cold water and drain well. Transfer to a bowl. Add snow pea sprouts and salad dressing and toss until combined. Pile on top of frittata. Serve.