Step 1

Preheat oven to 375 degrees F (190 degrees C). Grease a 9-inch pie dish with cooking spray.

Step 2

Line the prepared pie dish with puff pastry, covering base and sides. Trim excess pastry. Brush bottom with Dijon mustard.

Step 3

Melt butter in a saucepan over medium heat. Add chopped onions and cook until tender, about 5 minutes. Add garlic and cook 1 minute more. Mix in broccoli; cook 3 more minutes.

Step 4

Whisk heavy cream, eggs, salt, nutmeg, black pepper, and Italian seasoning in a bowl.

Step 5

Layer broccoli mixture over the puff pastry and top with Brie cheese slices. Pour in egg mixture.

Step 6

Bake in the preheated oven until set and golden, about 30 minutes.