These are Red Bean Jam cookies. My sister discovered the recipe. It’s so good, I made them four times in two weeks.
In case you don’t read Japanese, here’s the recipe:
1 stick of unsalted butter, 10g of sugar, 20g of condensed milk, 60g of red bean jam (or your favorite jam), and 170 g of flour. Mix in the order listed above and bake for 20 minutes at 350 degree.
*I like baking them for 25 to 30 mins.