this tartlet is essentially french onion soup on puff pastry, crowned with parmesan and mozzarella cheese.
1. 2 tablespoons olive oil
2. 2 tablespoons butter
3. 1 large white onion, sliced
4. 1 clove garlic, minced
5. 1/4 cup white wine
6. 1/2 cup beef broth
7. 1 teaspoon dried thyme
8. 1/2 teaspoon kosher salt (such as Diamond Crystal®)
9. 1/4 teaspoon ground black pepper
10. 1 sheet puff pastry
11. 1/2 cup grated Parmesan cheese
12. 1 cup shredded mozzarella cheese
Prep:10 Minutes, Cook:30 Minutes, Ready In:40 Minutes
1. preheat oven to 400 ranges f (two hundred tiers c).
2. warmness olive oil and butter collectively in a skillet over medium-high warmth until the butter is melted, 2 to 3 mins. saute onion and garlic inside the warm oil combination until the onion starts to caramelize, 15 to 20 mins.
3. pour white wine over the onion mixture; bring to a simmer and cook until fragrant, approximately 2 minutes. add pork broth and thyme; cook dinner until the liquid reduces in quantity through half. season the aggregate with kosher salt and black pepper.
4. trim puff pastry and in shape right into a tart pan. score a rim along the threshold of the pastry. puncture the center of the pastry with a fork. unfold the onion aggregate over the pastry; pinnacle with parmesan cheese and mozzarella cheese.
five. bake in preheated oven until the crust is golden brown, 15 to 20 minutes.