3 eggs
150 ml sour cream
2 cloves garlic, crushed
1 tablespoon chopped thyme leaves
75 grams blue vein cheese

Pre-heat oven to 180°C.
Cut the onions into four or six (depending on size) through the root end and place in a baking dish (lined with baking paper) with the vinegar, olive oil and salt and pepper. Roast for 30-40 minutes or until tender, turning at least once.
Put flour, salt and butter in food processor and combine till fine crumbs. Add egg yolk and water and process until the pastry comes together in a ball. Grease a 26 cm loose-based tin with butter. Roll out pastry and line tin. Rest pastry in fridge for 20 minutes.
Bake pastry blind for 20 minutes, then remove baking paper and bake for another 5 minutes.
While the pastry is baking, whisk together all the filling ingredients, except the blue vein cheese.
Arrange the onions in the pastry case, then gently pour the filling over. Break the blue vein cheese into pieces and place around the onions.
Bake for 30-40 minutes until the filling is golden and set.