Mix flour, butter, egg, salt, and milk together and knead until it forms a ball
Roll out the dough and mold it into the pan
Sauté onions and garlic in butter over low heat until fragrant
Add sugar and salt to the onions and continue sautéing until soft, translucent, and light brown
Add fresh thyme to the caramelized onions
Layer the caramelized onions on top of the dough in the quiche pan
Crumble goat cheese evenly across the pan
Whisk together milk, cream, eggs, salt, and pepper
Pour the cream and custard filling into the quiche pan
Sprinkle grated Emmental cheese on top
Bake in preheated oven at 200°C for 30-45 minutes until custard is set
