Flaky bites with apples, beer caramelized onions and Gruyere

Ingredients

• 1 giant Vidalia onion, cut in half then finely sliced
• Olive oil
• 4 Cortland apples, peeled and cored, cut in thin slices
• 1/3 cup Éphémère Apple beer by Unibroue
• 1 tablespoon maple syrup
• 2/3 pinches fennel seeds
• 450g flaky dough, thawed and very cold
• 2 cups Gruyère cheese, grated
• Salt and ground pepper