Gratin de pâtes au thon

03 — Method

1. Preheat the oven to 200 °C (400 °F) fan. Bring a large pot of salted water (10 g per liter) to a rolling boil.
2. Drain the tuna, keeping a little of the oil, and flake roughly with a fork.
3. Finely dice the onion. Remove the germ from the 3 garlic cloves and chop them. Chop half the basil, keeping the rest whole to garnish.
4. Heat 3 tbsp of olive oil in the large sauté pan over medium heat and soften the onion for 5 minutes. Add the garlic and dried oregano and cook 1 minute.
5. Add the canned tomatoes, crushed with a fork, and simmer for 15 minutes, stirring often, until thick.
6. Cook the 400 g (14 oz) of pasta 2 minutes less than the package says (they’ll finish in the oven). Drain, saving 100 ml (½ cup) of the cooking water.
7. Stir the tuna, olives, capers and crème fraîche into the sauce. Add the pasta and chopped basil and mix gently.
8. Pour into the large buttered gratin dish and sprinkle generously with Gruyère and Parmesan. Bake for 25 minutes at 200 °C (400 °F) until golden and bubbling.