1 Heat 1 tbsp oil and the butter in a large saute or frying pan. Add the onions and cook on a fairly high heat, stirring constantly until they begin to soften but not brown.

2 Reduce the heat and continue to cook over a medium heat, stirring frequently so the onions do not stick or brown.

3 The onions need about 30 minutes in total to caramelise. Stir in the thyme and garlic five minutes before the end of cooking time. Tip into a large bowl and cool for at least five minutes. Season generously.

4 Preheat the oven to 180c/350f/Gas 4. Add the eggs, Parmesan and sage to the onions and stir well to combine - you should have 1.2 litres/2 pints of mixture in total.

5 Heat the remaining oil in an oven- proof heavy-based 23cm/9" pan, deep enough to take the mix. Swirl to coat the pan sides evenly, add the egg mix and cook for two minutes over a low heat to set the bottom and sides.

6 Scatter over the goats' cheese and cook gently for five minutes. Cook the pan uncovered in the oven for about 20 minutes until just set, puffed up and lightly golden.

7 Loosen the sides with a palette knife and cut the frittata into wedges. Serve warm or cold, straight from the pan with a good dollop of the salsa.