Preheat the oven to 350°F. Line two baking sheets with parchment., In the bowl of your mixer combine the butter, peanut butter, brown sugar, and vanilla. Beat on medium high speed until lightened and fluffy., Add in the eggs and liquid milk, mix until well combined. Be sure to scrape the bottom and sides of the bowl once or twice., On low speed mix in the flour, dried milk, cinnamon, and salt. Mix until the dough is cohesive. Add 4 1/2 cups total of your favorite add ins and mix until all are incorporated., Scoop 1/4 cup (about 70g each) mounds of batter 2" apart on the parchment-lined sheets; A scone and muffin scoop works great for this. Slightly flatten each mound. This recipe contains no leaveners, so the cookies will only spread and rise slightly., Bake the breakfast cookies for 18 to 22 minutes, until lightly browned. Do not over-bake or the cookies will be dry and crumbly. Cool on cookie sheets for 5-8 minutes. Move to a rack to cool completely. , Storage leftover breakfast cookies in an airtight container at room temperature for several days. Freeze for longer storage.