Melt the butter in an 18 cm (7 in) diameter non-stick omelette pan and fry the mushrooms with the garlic until they are a deep golden brown and beginning to go crisp around the edges. Add the sun-dried tomatoes and stir over the heat for 1 to 2 minutes. Meanwhile, preheat the grill.

Roughly spread the mushroom mixture over the base of the pan. Beat 2 tablespoons of cold water into the eggs and season with pepper (both feta cheese and sun-dried tomatoes can be salty, so no extra salt should be needed to season the omelette). Pour this over the mushrooms, gently swirling the pan to spread the eggs. Leave to set, undisturbed, on a low heat for 1 to 2 minutes, then sprinkle over the feta. Place the pan under the hot grill for about 1 to 2 minutes or until the eggs are lightly cooked and the feta cheese is just beginning to melt.

Sprinkle the omelette with black pepper and scatter with fresh thyme sprigs, to garnish. Cut into wedges and serve immediately.