This is my take on the German classic, zwiebelkuchen, which basically translates as onion cake. My version is a bit richer with the addition of gruyere and also has a twist with the smoked mussels - though it's delicious without them as well.
Sour cream pastry
250g plain flour
150g butter, chilled and diced
1 tsp salt flakes
2 tbsp sour cream
100g smoked speck, finely diced
30g unsalted butter
4 cloves garlic, finely sliced
4 white onions, finely sliced (about 350g)
350g sour cream
1 tbsp plain flour
coarsely grated salt flakes
freshly ground black pepper
2 tsp smoked paprika
18-20 smoked chilli mussels (you can buy these vacuum-packed)
1/2 bunch dill, picked and chopped
1. Preheat the oven to 165C fan-forced or 185C conventional.
2. In a saute pan over medium heat, cook the speck until it starts to brown. Add the butter, garlic and onion and gently cook for 15-20 minutes or until soft and translucent but not browning. Set aside to cool.
3. While the onions cook, whiz the flour, butter and salt in a food processor to a sandy crumb. Add the egg and sour cream and process until it starts to form a ball. Form into a round between two sheets of baking paper and chill for half an hour.
4. When you are ready to bake the tart, in a large bowl whisk together the eggs, sour cream and flour, add the gruyere and the garlic and onion mix, season lightly with salt and pepper and mix through.
5. Roll chilled pastry into a rough rectangle and place on a baking tray on baking paper. Pour mix on to the pastry (mix will be stiffish and malleable), leaving a border around the edge of three to four centimetres. Fold edges up, crimping corners together to make a free-form tart. Sprinkle with paprika. Bake 30-40 minutes or until golden. Cool to room temperature.
6. To serve, toss the mussels through the dill with a squeeze of lemon. Cut the tart into portions, top with the mussels, serve.
Drink a good weissbier