Caramelised Onion and Gruyère Tart - Seasonal Recipe

Caramelised Onion and Gruyère Tart

🌍 Seasonal, Autumn Difficulty: ●●●○○

Alsatian onion tart (Zwiebelkuchen) and its cousin quiche are rooted in the borderland between France and Germany, a region where culinary traditions merged over centuries; the combination of low-and-slow-cooked onions with aged cheese is one of the great flavour alchemies of European cooking.

Ingredients

• 250g (2 cups) all-purpose flour
• 125g (½ cup + 1 tbsp) cold butter, cubed
• 1 egg yolk
• 3–4 tbsp ice water
• Pinch of salt
• 1 kg (990g (2.2 lbs)) onions (about 5 large), thinly sliced
• 3 tbsp unsalted butter
• 1 tbsp olive oil
• 1 tbsp fresh thyme leaves
• 1 tsp sugar
• 2 tbsp balsamic vinegar
• 3 eggs
• 240ml (1 cup) heavy cream
• 200g (7 oz) Gruyère, grated
• Salt and pepper

Method

1. Making — Make pastry: process flour, salt, and butter; add egg yolk and water to form dough. Rest 30 minutes. Roll and line a 25cm (10 in) tart pan. Blind-bake at 190°C (375°F) for 15 minutes; remove weights, bake 5 more. Cool.
2. Caramelising — Caramelise onions: melt butter and oil in a large, heavy pan over medium-low. Add onions, salt, and thyme. Cook slowly, stirring every 10–15 minutes, for 45–60 minutes until very soft and deep golden-brown. Add sugar and balsamic in the final 10 minutes. Cool.
3. Whisking — Whisk eggs, cream, and ¾ of the Gruyère. Season. Fold in onions.
4. Pouring — Pour into tart shell. Top with remaining cheese.
5. Baking — Bake at 180°C (350°F) for 30–35 minutes until set and golden. Rest 15 minutes before slicing.

Tags: all-purpose flour, cold butter, egg yolk, –4 tbsp ice water, pinch of salt · Source: Brittani's Almanac