Add butter cubes and blend until the mixture resembles coarse meal, about 30 seconds. (lanascooking.com)
Add cold butter cubes and cut in with pastry cutter or two knives until mixture looks like course crumbs. (eatpicks.com)
With the mixer running, add in the softened butter cubes a few at a time, allowing them to mix into the dough before adding more. (korenainthekitchen.com)