Sure, you've had oatmeal in a sweet, but these cookies also contain spelt flour, which has a nutty, slightly sweet flavor. A dark-chocolate coating and a sprinkling of flaky salt make the ideal finishing touches.
Whisk together spelt flour, oats, and salt. Beat together butter and sugar on high speed until fluffy, about 3 minutes. Add egg and vanilla; beat to combine. Reduce speed to low; add flour mixture to combine. Gather dough in plastic wrap; form into a rectangular disk and refrigerate until firm, at least 1 hour and up to 1 day.
Preheat oven to 325 degrees. On a floured surface, roll out dough to a scant 1/2-inch thickness; cut into 2-inch squares. Place 1 inch apart on two parchment-lined baking sheets. Bake until firm to the touch and golden around edges, 24 to 26 minutes. Let cool completely.
Melt chocolate. Dip each cookie diagonally in chocolate; sprinkle with flaky salt, if desired. Refrigerate on parchment-lined sheets until just set.
For clean chocolate-dipped edges, move cookies around a few times while chocolate sets to avoid excess puddling.
If you can't find spelt flour, whole-wheat flour works great here in its place.