Preheat oven to 350°F (175°C). Grease an 8x8 inch pan. Whisk flour, sugar, cocoa, baking powder, baking soda, and salt together. Mix in milk, oil, egg, and vanilla until smooth, then stir in hot coffee. Pour into pan and bake 18-22 minutes until a toothpick comes out with a few moist crumbs. Cool completely.

Crumble the cooled cake in a food processor until it looks like damp sand, or rub it fine by hand in a large bowl.

Beat butter, powdered sugar, milk, vanilla, and salt into a fluffy buttercream. Mix 2 tbsp into the crumbs and add more a little at a time until the mixture holds together when squeezed.

Roll tablespoons of the mixture into 1-inch balls and place on a parchment-lined sheet. Chill for at least 30 minutes until firm.

Melt candy melts in a deep bowl. Dip the tip of each stick into the chocolate, insert into a cake ball, and chill 5 minutes. Dip each pop straight into the melted coating, tap off excess, and decorate with sprinkles. Stand upright to set.