Prepare the Dough: In a large mixing bowl, combine warm milk, sugar, and yeast. Allow it to sit for about 5 minutes until bubbly. Next, add egg, melted butter, and flour, mixing until a shaggy dough forms.

Knead the Dough: Transfer the mixture onto a lightly floured surface. Knead the dough for about 10-12 minutes until smooth and elastic.

Divide and Shape: Divide the dough into 10 equal pieces, roll each into a ball, then flatten slightly and encase a cube of cold butter. Pinch the seams to seal and place each bun seam-side down on a lined baking tray.

Proof the Dough: Cover the shaped buns with cling film. Allow them to proof in a warm area for 75-90 minutes until doubled in size.

Prepare the Topping: While your buns rise, mix softened butter and sugar until light and fluffy. Gradually add coffee powder and flour until just combined.

Pipe the Topping: Fit a piping bag with a round tip, fill it with the coffee topping, and pipe it onto each bun.

Bake: Preheat your oven to 350°F (175°C) and bake for 18-20 minutes until golden brown.