CARAMELISED ONIONS

1. Heat a large, heavy bottomed pan over high heat. Add about 2 Tbsp oil, and the onions, stirring to coat. Add a big pinch of salt. Reduce the heat slightly, and cook for about 10 minutes, stirring occasionally. After 10 minutes, add the sugar, and stir well. 
2. Continue to cook the onions for a further 30 to 40 minutes, reducing the heat as necessary and stirring every few minutes. Add a little extra oil or water if needed to stop the onions drying out. 
3. The onions are done once they are collapsing, and dark brown in colour. They will have reduced significantly. 
4. Deglaze the pan with the balsamic vinegar, and stir well. Remove from the heat and allow to cool.

CRUST

1. Preheat the oven to 350˚f. Roll out the dough to ¼" thickness and use it to line a 9" round Tart tin with a removable bottom, trimming the excess. Line tightly with foil, and fill with ceramic pie weights, rice, or beans.
2. Bake for 15 minutes, until the pastry has set and is beginning to go golden. Remove from the oven, remove foil and weights, leave to sit for 5 minutes, then brush all over with egg wash. Return to the oven for another 5 minutes. Remove from the oven and allow to cool completely on a wire rack.

ASSEMBLY AND BAKING

1. In a medium bowl, whisk together the cream, eggs, and salt and pepper. Blanch the asparagus in boiling water for 15-20 seconds. Drain and run under cold water. Spread the caramelised onions over the bottom of the prepared tart crust using your hands or an offset spatula. Crumble the goat's cheese over the onions. Pour the egg mixture over the onions and goat cheese, taking care not to overfill.
2. Arrange the asparagus on the surface of the tart, with all of the spears pointing in the same direction. You will most likely have to double up on the layers to fit it all in. Bake the quiche for 30-35 minutes, until the filling is set and golden. Remove from the oven and allow to cool. Serve warm or at room temperature.