Chocolate-Crust Tart Shell from Back to Baking by Anna Olson

Ingredients

• ¼ cup (60 mL) regular or Dutch process cocoa powder
• 1 cup (250 mL) all-purpose flour
• 6 Tbsp (90 mL) cool unsalted butter, cut in pieces
• 1 egg yolk
• ¼ cup (60 mL) packed light brown sugar
• ¼ tsp (1 mL) salt
• 1 tsp (5 mL) vanilla extract
• 2 Tbsp (30 mL) milk