Raspberry-Saskatoon Galette - Dinner With Julie

Ingredients

• 1/2 pkg puff pastry dough or pastry for a single crust pie
• flour, for rolling
• 1/3 cup sugar
• 2 Tbsp cornstarch
• pinch salt
• 3 cups raspberries and saskatoons
• 1 Tbsp butter, in bits (optional)
• milk or cream, for brushing (optional)
• coarse sugar, for sprinkling (optional)