Gouda adds a creamy texture and mild flavor, but mozzarella or cheddar can be used instead. If flipping feels difficult, skip it: cover the pan with a lid and let the omelette cook on one side until the top is set. Omelettes have the nicest texture fresh, but leftovers can be refrigerated in an airtight container for 1 to 2 days.
Keyword cheesy omelette, Gouda omelette, mushroom omelette, spinach and mushroom omelette