1 tsp duck fat
6 large yellow onions, sliced
12 white anchovies (white anchovies are milder in flavour than the darker, saltier black anchovies, but you can easily use black at a pinch)
1 sheet puff pastry
12 Niçoise olives
- Note: Cassis prepare the onions at least a day in advance to allow the rich, caramelized taste to really come through.
- Melt duck fat in a heavy-based pot or Dutch oven over medium heat. Add onions and cook slowly, stirring every few minutes with a wooden spoon, working and scraping the bottom of the pot.
- When onions are soft and beginning to colour (about 30 minutes), turn the heat up a little and continue scraping the bottom of the pot as it cooks. Cook until onions turn a rich, dark amber colour. You’ll know the onions are done when a clear fat begins to separate from the onions. Pour off fat and cool onions (these will keep up to five days in the refrigerator).
- Cut the sheet of pastry into four, and line buttered tart shells. Fill tarts with onion mixture, and cook for 25 minutes at 375º F.
- Remove tarts from oven. Add three anchovies per tart, and place back in oven for another 10-15 minutes or until the tarts are cooked (look underneath to check).
- Rip olives in half, and add six halves to each tart. Serve with arugula salad.