Chorizo and vegetable frittata

Ingredients

• 4 baby potatoes, quartered
• 1 tablespoon vegetable oil
• 1 medium red onion, cut into thin wedges
• 2 chorizo sausages, thinly sliced
• 1 medium red capsicum, coarsely chopped
• 1 medium green capsicum, coarsely chopped
• 1 medium zucchini, thinly sliced
• 6 eggs, at room temperature
• 1/2 cup milk
• 1/2 cup grated tasty cheese
• 1 tablespoon chopped flat-leaf parsley
• mixed salad, to serve