Soften 35g unsalted butter at room temperature using a spatula.

Add 40g sugar to the softened butter and mix until the sugar is no longer visible.

Combine 4g instant coffee with 7g hot water, then add it to the mixture.

Add 27g egg at room temperature and whisk quickly.

Sift 40g cake flour into the mixture and mix until no flour is visible.

Spread 5g salted butter on each slice of bread (2 slices).

Place another slice of bread on top of the buttered slices.

Pipe the mochabun base in a zigzag pattern on top of the bread using a piping bag.

Place the prepared mochabun toast on a baking tray lined with parchment paper.

Bake in a preheated oven at 180°C for 13 minutes.