The shells for these tartlets are made by pressing pieces of bread into muffin tins. The shells are brushed lightly with melted butter and baked until crisp. They are then filled with a mixture of onions and sun-dried tomatoes. Both the shells and the filling can be prepared ahead, then warmed and assembled for serving.
Preheat the oven to 450°F (230°C). Lightly spray a 12-cup muffin tin with cooking spray. Using a 3-in. (7.5-cm) pastry cutter, cut a disc from each slice of bread. Flatten each bread disc with a rolling pin, then press into the muffin cups to line them evenly, curving the edge of the bread slightly to make large scallop shapes.
Brush the bread cases with the melted butter and bake until crisp and golden, about 8 to 10 minutes. Set aside in a warm place until ready to fill. (If made ahead, keep the bread cases in an airtight container.)
Heat the oil in a large, heavy skillet. Add the onions and stir well. Cover with the lid and cook over a low heat for 20 minutes or until the onions are very soft.
Remove the lid, turn up the heat and cook rapidly, stirring, until the onions turn a dark golden brown. Remove from the heat and stir in the sun-dried tomatoes and thyme. Season lightly with salt and pepper. (If made ahead, cool the filling and keep in the fridge, then reheat just before filling the bread cases.)
Divide the onion filling among the bread cases, then sprinkle the chopped walnuts over the top. Serve hot.
Each serving (one tart) provides: calories 83, calories from fat 45, fat 5 g, saturated fat 1 g, cholesterol 3 mg, carbohydrate 8 g, fibre 1 g, sugars 3 g, protein 2 g Choices per serving: Carbohydrate 1⁄2, Fat 1