Sweet onion and cauliflower tart

Name: Sweet onion and cauliflower tart
Cuisine: British
Ingredients: Glug light olive oil for frying; 1 onion, sliced; 1 tsp brown sugar; 25g butter; 1 small cauliflower, separated into florets; 1 fresh bay leaf; 250ml whole milk; 150g wensleydale cheese, grated; 50g pitted black olives, chopped; 4 fresh thyme sprigs, leaves picked; 3 medium free-range eggs; 100ml double cream; 200g plain flour, plus extra to dust; 4 fresh thyme sprigs, leaves picked and roughly chopped; 100g cold butter, cubed; 3-4 tbsp ice-cold water; 23cm fluted tart tin