Marusei Butter Sandwich

1. Prepare the rum raisins: In a small bowl, combine raisins and dark rum. Let them soak for at least 30 minutes, or preferably overnight in the refrigerator.

2. Make the cookie dough: In a large bowl, cream 150g unsalted butter (for cookies) and 80g granulated sugar (for cookies) until light and fluffy. Beat in 20g egg yolk (for cookies) until well combined.

3. Sift cake flour, baking powder, and salt into the butter mixture. Mix gently with a spatula until just combined and a dough forms. Do not overmix.