In a pot add in butter, milk and Chekhup Hokkaido Milk Latte together and simmer it.
Once the butter are melted and the coffee are well combined transfer it into the flour bowl and stir it.
Add in egg yolk and mix.
In another bowl beat egg whites and sugar together until soft peaks.
Combine both batter until well combined.
Bake in 150c oven using water bath method for one hour