1 1/2 cups all-purpose flour, plus more for work surface
3/4 cup unsweetened Dutch-process cocoa powder
1/4 teaspoon coarse salt
1/4 teaspoon finely ground pepper
1 tablespoon plus 1 teaspoon good quality instant espresso powder
1/2 teaspoon ground cinnamon
3/4 cup (1 1/2 sticks) unsalted butter, softened
1 cup granulated sugar
1 large egg
1 tablespoon milk
1 1/2 teaspoons pure vanilla extract
Chocolate Whipped Cream
Whisk together flour, cocoa powder, salt, pepper, espresso powder, and cinnamon in a large bowl; set aside.
Put butter and granulated sugar in the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until pale and fluffy, about 3 minutes. Mix in egg, milk, and vanilla. Reduce speed to low. Add flour mixture; mix until just combined. Divide dough in half and wrap each piece with plastic wrap; refrigerate at least 1 hour and up to overnight.
Preheat oven to 350 degrees. Roll out dough 1/4 inch thick on a lightly floured surface. Brush any excess flour off dough with a dry pastry brush. Cut dough using a 2 1/2-inch heart-shaped cookie cutter. Transfer heart shapes to baking sheets lined with parchment paper or a nonstick baking mat, spacing 1 inch apart.
Bake cookies until there is a slight resistance when you lightly touch the centers, about 10 minutes. Transfer cookies to wire racks to cool completely.
Fill a pastry bag fitted with a 1/2-inch plain tip with the chocolate whipped cream. Pipe cream onto half of the cookies; top with remaining cookies.
Whipped Cream
4 ounces milk chocolate, coarsely chopped
2 cups heavy cream
3 tablespoons sugar
Place chocolate in a medium bowl; set aside.
Heat sugar and 1 cup cream in a small saucepan over medium heat. Cook until sugar has dissolved.
Pour cream mixture over chocolate; stir until chocolate has melted. Let cool.
Transfer chocolate mixture to an electric mixer fitted with the whisk attachment. Add remaining cup heavy cream and beat on medium speed until thick and fluffy.