Cut 1 stick unsalted butter into 8 pieces and place in the bowl of a stand mixer. (Alternatively, place in a large bowl if using an electric hand mixer.) Let sit at room temperature until softened.

Arrange 2 racks to divide the oven into thirds and heat the oven to 350°F. Line 2 baking sheets with parchment paper.

Place 1 cup flour of choice, 1 teaspoon baking powder, 1 teaspoon ground cinnamon, ¾ teaspoon kosher salt, and ¼ teaspoon ground nutmeg in a medium bowl and whisk to combine.

Add ¼ cup honey or maple syrup and ¼ cup nut or nut-alternative butter to the bowl of softened butter. Beat with the paddle attachment on medium-high speed until lightened in color, 2 to 3 minutes. Unless your butter is very soft, some small pieces of butter may remain visible — that is OK. Add 1 large egg and 1 tablespoon vanilla extract and beat just until combined, about 1 minute.

Turn the mixer off and scrape down the sides of the bowl. Add the flour mixture and beat on low speed until incorporated, about 30 seconds. Add 2 cups rolled oats, 1 cup chunky mix-ins, and ¼ cup sweet mix-ins. Stir by hand to combine.

Scoop out the dough into ¼-cup portions and place at least 2 inches apart on the prepared baking sheets, 8 per sheet. Flatten each ball of dough lightly with the palm of your hands until about 1-inch thick. If desired, press a few extra mix-ins onto the top of the cookies.

Bake for 7 minutes. Rotate the baking sheets between racks and from front to back. Continue to bake until the bottoms and edges of the cookies are lightly browned, 5 to 7 minutes more (they are best slightly underbaked). Let cool completely on the baking sheets.