Preheat oven to 350 degrees. Line baking sheets with parchment paper.
In a mixing bowl; cut butter into flour using a pastry blender or two forks.
Lightly mix in water with a fork; until well combined.
In a mixing bowl; combine tsubushian with oil.
On work surface; for dough into 1-inch balls; flatten into a circle.
Fill with teaspoonful of tsubushian mixture.
Fold dough edges around filling and pinch to seal.
Place seam side down onto prepared pan.
Lightly brush tops with milk.
Bake 35-40 minutes until lightly browned.