Step 1: Preheat your oven to 350°F (175°C).
Step 2: In a large mixing bowl, cream together the softened butter and peanut butter until smooth. Gradually add in the sugar and brown sugar, mixing until fluffy.
Step 3: Crack in the eggs one at a time, mixing well after each addition. Pour in the vanilla extract and continue mixing until well incorporated.
Step 4: In a separate bowl, whisk together the dry ingredients: instant nonfat dry milk, all-purpose flour, baking soda, and salt. Gradually add this to the wet mixture, mixing on low speed until just combined.
Step 5: Using a cookie scoop or tablespoon, drop rounded balls of dough onto prepared baking sheets, spacing about 2 inches apart.
Step 6: Bake in the preheated oven for 10-12 minutes, or until edges are lightly golden.
Step 7: Let cookies cool on the baking sheets for 5 minutes before transferring to a cooling rack.
