Autumn Apple Galette

Ingredients

• 4 cups apples, peeled and cored and sliced thin (gala, ambrosia, or granny smith are best!)
• 1/3 cup brown sugar
• 1 tbsp all purpose flour
• 1/2 tsp cinnamon
• 1/8 tsp kosher salt
• 1/2 tsp pure vanilla extract
• 1 tsp fresh lemon juice
• 1 tbsp cold unsalted butter, cut into small cubes
• 1 package puff pastry (1 large or two small sheets) thawed and kept cool in fridge
• 1 egg, beaten
• 1 tsp either granulated or coarse sugar