To create this decadent tart, sweet spring bulb onions get cozy with mustard, balsamic vinegar and honey. A generous shower of Gruyere cheese over the pastry ensures a crisp, golden-bottomed crust. Serve with a simple tossed salad or grilled asparagus.
- Prep time 25 minutes
- Total time 1 hour & 30 minutes
- Portion size 8 servings
Unroll puff pastry; press into fluted 9-inch (23 cm) tart pan with removable bottom. Line with foil; fill with pie weights or dried beans. Bake on bottom rack in 400 F (200C) oven for 20 minutes. Remove weights and foil; let cool in pan on rack.
Meanwhile, in skillet, heat oil over medium-high heat; cook onions, stirring, until golden, about 3 minutes. Add 1/4 cup water; reduce heat to medium. Cover and cook, stirring occasionally, until no liquid remains and onions are soft, about 5 to 8 minutes.
Stir in vinegar, honey and half each of the salt and pepper; cook, stirring, until onions are dark golden, about 8 minutes. Remove from heat; stir in 3/4 tsp of the thyme. Set aside.
Stir together egg, cream, mustard, and remaining salt and pepper. Sprinkle bottom of pastry with half of the Gruyere cheese; top with onion mixture. Pour egg mixture over top; sprinkle with remaining cheese and thyme.
Bake in 400 F (200 C) oven until crust is golden and knife inserted in centre comes out clean, about 25 minutes. Let stand for 10 minutes before cutting into wedges.
Nutritional facts per each of 8 servings: about
- Fibre 2 g
- Sodium 261 mg
- Sugars 4 g
- Protein 9 g
- Calories 243.0
- Total fat 16 g
- Cholesterol 57 mg
- Saturated fat 8 g
- Total carbohydrate 17 g
- Iron 11.0
- Folate 14.0
- Calcium 20.0
- Vitamin A 15.0
- Vitamin C 10.0