1 Mix the dry ingredients: In a medium mixing bowl, combine the flour, milk powder, salt, and baking soda and whisk to mix. Set aside.
2 Beat the sugars and the butter: With an electric mixer or in a stand mixer with a beater attachment, beat together the granulated sugar, brown sugar, and softened butter on medium speed until combined, 30 to 60 seconds. Pick out any large pebbles of hard brown sugar that you see. Scrape down the sides of the bowl and the beaters.
3 Mix in the eggs and vanilla: Add the two eggs and vanilla to the butter-sugar mixture and beat at medium speed until no clumps or streaks remain, 10 to 20 seconds. Scrape down the sides of the bowl and the beaters.
4 Mix in the flour mixture: Add the flour mixture all at once. Beat on low speed just until no more dry streaks of flour are visible, 20 to 40 seconds. You may still see some flecks of milk powder…