Preheat oven to 350F and line baking sheets with parchment paper.

Add the flour and oatmeal to a medium bowl. Stir to combine, then set aside.

Fill a small bowl with water and get a fork ready. Set aside.

Use an electric handmixer to cream together the softened butter and sugar until light and fluffy. Add the egg and vanilla extract, then beat until completely blended.

Pour the flour and oat mixture into the creamed mixture all at once. Beat with electric handmixer until all ingredients are combined, but do not overmix.

Drop rounded ½ teaspoons** of dough onto the prepared baking sheets. You should be able to fit 8 cookies comfortably on a baking sheet – keep in mind that they will spread a little in the oven.

Then, dip the fork in water and lightly flatten each ball of dough with the back of the wet fork. Sprinkle on sanding sugar, if desired.

Bake cookies at 350F for 9-10 minutes, until lightly brown on the edges.

Remove cookies from oven and let rest on the baking sheet for one minute, then carefully transfer cookies to a wire rack to cool completely. Cookies will still be very soft at this stage, but they will cool and harden quickly.

Store in an airtight container. These also freeze really well.