Preheat the oven to 350°F (176°C). Line a cookie sheet with parchment paper or a silicone baking mat.

Cream the butter and sugars together until light and fluffy, about 3-4 minutes.

Add the egg and vanilla extract and mix until well combined.

In a separate bowl, combine the flour, baking soda, baking powder and salt. Add the dry ingredients to the butter mixture and mix until well combined.

Stir in the oats, then add your mix-ins (pecans, toffee bits, raisins, dried cranberries, chocolate chips, white chocolate chips, and butterscotch chips) and stir until evenly distributed.

Refrigerate the cookie dough for at least 5 hours and up to 3 days.

Make balls of cookie dough about 2 tablespoons in size.

Place the balls of cookie dough onto the lined cookie sheet and bake for 10-12 minutes. Cookies will spread a bit and may look a little undercooked when you remove them, but they’ll continue to cook and firm as they cool.

Remove the cookies from the oven and allow to cool on the cookie sheet for 3-5 minutes, then remove to a cooling rack to finish cooling.

Once cooled, store cookies in an air-tight container.