To prepare a homemade trail mix cookie recipe, first you need to gather your ingredients. First, you'll need: 1 pound of rolled oats, 1 cup of brown sugar, and 1 teaspoon of baking powder. You will also need 3 tablespoons of butter, 1/2 cup confectioners' sugar and 1/2 teaspoon vanilla extract. If you don't have any of these ingredients, then you can use granulated sugar. Then, add your dry ingredients to the wet ingredients and mix until everything is evenly combined. Now, it's time for the fun part! Bake the cookies at 350 degrees F for 12-15 minutes, or until the edges are golden brown and the center is just set. Remove from the oven and let cool for 5 minutes before transferring them to an airtight container and storing them in the refrigerator until you are ready to eat them.