Sugar Cookies Filled with Blue Milk Mochi (Mochi-kie)

Make the Mochi:

Mix together the glutinous rice flour, butterfly pea flower powder, and sugar. Gradually stir in the milk until the mixture forms a smooth batter. Cover the bowl with plastic wrap and steam on high heat for 25 minutes. Stretch the dough a couple of times when cooled. Form into small dough balls (~10g each).

Make the Sugar Cookie Dough:

Cream together butter and sugar until light in texture. Beat in the egg and teaspoons of vanilla extract. In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the flour mixture to the butter mixture and mix until just combined.

Assembly and Baking:

Take small portions of the cookie dough, fold a ball of blue mochi inside the cookie dough, and flatten the surface. Bake at 350F for 15 minutes.