Step 2

Melt 30g of butter in a large pan. Add the shallots, carrots, and celery and gently fry until soft. Add the garlic and cook for 1 minute.

Step 3

Pour the filling into a 20×30cm ovenproof dish. Spoon and spread the mashed potato evenly over the top. Grate over the Gruyère.

Step 4

Pour in the white wine and cook for 1 minute. Stir in the tomato purée, chopped tinned tomatoes, and stock. Cook for 10–15 minutes until the sauce thickens.

Step 5

Stir in the shredded chicken, olives, and parsley. Season to taste with salt and pepper.

Step 6

Preheat the oven to 180°C/160°C fan/Gas 4.

Step 7

Bake for 30–35 minutes, until piping hot and the potato topping is golden-brown.