I've tried this most people's favorite - Mexican Bun. Just use any sweet bun or sweet dough recipe. Fill in with cubed butter and sprinkle with sugar. Close the edge properly and neatly. Topped the buns with coffee paste toppings.
This is my version of Mexican Bun's Topping
1 tbsp cappucino emulco
Mix all together. Using piping bag, pipe as circle direction from inside to outside.