1) Preheat the oven to 350°F. Line two baking sheets with parchment paper.
2) In the bowl of your mixer combine the butter, peanut butter, brown sugar, and vanilla. Beat on medium high speed until lightened and fluffy.
3) 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.
4) On low speed mix in the flour, Hi Maize fiber, 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.
5) Scoop generous 1/4 cup mounds of batter 2 inches apart on the parchment lined sheets. Slightly flatten each mound. This recipe contains no leaveners, so the cookies will only spread and rise slightly.
6) Bake the 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. Yield: 18 to 20 cookies, depending on size.
The nutritional analysis below was made with the following add-ins: 1 cup each: rolled oats, granola, dried cranberries, and chocolate chips, and 1/2 cup of shredded sweetened coconut. Using whole wheat flour adds 1/2 gram of fiber per serving and doesn't change any of the other amounts per serving.