Yield: makes 3 mini loafs
Preheat oven to 350 degrees F.
In a mixer, cream the butter and sugar with the paddle attachment for about 3 minutes on medium speed. It should look pale.
Lightly whisk together the eggs and vanilla paste. Slowly add to butter mixture at low speed until combined.
Sift together flours, baking soda, baking powder and salt. Add the dry mixture to the wet in three additions, alternating with the sour cream. Mix well.
Divide the batter into two bowls. Add the matcha powder to one bowl and stir until batter not longer has any green streaks.
Alternate pouring in the cream colored batter and the matcha batter into the 3 mini loaf tins. When finished, take a knife and swirl the cream and matcha batter together.
Bake for 35-40 minutes or until toothpick comes out clean when inserted in center of loaf. Let rest on cooling rack for a couple minutes. Slice with cake knife or bread knife when cool to touch.