Mushroom and Spinach Frittata

Ingredients

• • 6 eggs
  • 1/4 cup (60 ml) milk
  • 1 cup (250 ml) grated cheddar cheese
  • 1 onion, thinly sliced
  • 4 oz (115 g) white button mushrooms, sliced
  • 3 tablespoons (45 ml) butter
  • 2 cups (500 ml) baby spinach
  • Salt and pepper