Preheat oven to 400 degrees.
Combine strawberries, sugar, cornstarch, black pepper, and vanilla extract and mix until evenly covered.
Turn dough onto a floured board and roll out until 1/4 inch thick.
Using a large heart-shaped cookie cutter cut eight hearts out of dough. Using a small heart-shaped cookie cutter cut a small heart in the center of four of the large hearts; these will be the tops. Place bottom pieces on baking sheet and scoop a heaping tablespoon of strawberry mixture onto the hearts.
Brush the edges of the dough with egg white and carefully cover with top dough piece. It may be necessary to shape the middle heart as it can get slightly misshapen.
Brush top of the pie with beaten egg and use a fork to press the edges together.
Bake for 20-25 minutes or until pies are golden brown.
While pies are baking, use the small heart cookie cutter to cut out four marshmallow hearts. You can use store-bought large marshmallows, flattened and cut out, or homemade marshmallows. Once the pies are done baking, take them out of the oven and let them cool for 1-2 minutes and place a marshmallow heart in the center heart cut out.
Place the heart pies in the oven on broil mode and broil until roasted.