Apple Cinnamon Slab Pie

Bahan-bahan (4 porsi)

• 1 lb 2 large apples (I used granny smith apples), peeled, cored and cut into 1/3" slices
• 4 Tbsp unsalted butter
• 1/4 cup brown sugar (lightly packed)
• 1 tsp ground cinnamon
• 1 sheet (8 or 9 oz frozen puff pastry, thawed (I used Pepperridge Farms))
• All purpose flour for dusting
• 1 egg (lightly beaten for egg wash)
• Coarse sugar for sprinkling (I used raw sugar)