Preheat oven to 350 °F (180 °C). Grease a 9‑inch round cake pan, line the bottom with parchment paper.

In a large bowl, sift together flour, cocoa powder, baking powder, baking soda, and salt. Whisk in brown sugar and granulated sugar.

Add oil, buttermilk, egg, and vanilla extract; mix until combined. Dissolve instant espresso powder in boiling water and add to batter; mix until just combined—the batter will be thin.

Pour batter into the prepared pan. Bake for 28‑30 minutes or until a toothpick comes out clean and the top springs back when lightly touched. Let cake cool in pan for 30 minutes, then remove and cool completely on a wire rack.

In a stand mixer or with a handheld mixer, beat butter until smooth. Add powdered sugar, mix on low then medium until combined. Add cocoa powder and mix until well combined. Scrape down bowl; add milk and vanilla extract and mix on medium until fully combined.

Crumble the cooled cake into a mixing bowl or mixer bowl. Add about ½ cup of the chocolate frosting (reserve the rest for another use) and mix until the mixture resembles cookie dough. Roll mixture into 1‑tablespoon sized balls and place on a parchment‑lined baking sheet. Freeze for about 1 hour.

Melt chopped semi‑sweet chocolate and coconut oil in a microwave safe bowl, stirring every 30 seconds until smooth. Let the mixture cool slightly (~10 minutes). Remove 4‑5 cake balls from freezer at a time. Dip the end of a 4‑inch lollipop stick ~½ inch into the melted chocolate, then insert into center of a cake ball about ¾ of the way in. Then dip the cake pop into the melted chocolate so the entire pop (not the stick) is coated. Gently tap the stick a few times and rotate to remove excess. If using sprinkles/nuts, add them immediately after dipping. Place cake pop upright (in a Styrofoam block or similar) and allow to set. Repeat with remaining balls until all are coated. Let coated cake pops set at room temperature for at least 30 minutes.