Preheat oven to 300.
Cream butter, sugar, and vanilla until combined in a stand mixture with the paddle attachment. On slow speed, beat in flour and salt until combined. Flatten into a disk, wrap in plastic wrap and chill until firm, at least 2 hours or overnight.
On a lightly floured surface, roll dough to 1/16-to-1/8 inch thick. (Remember, these won’t rise, so where they are raw is basically where they’ll be cooked.)
Cut out hearts with a 2-inch heart cookie cutter. Transfer cookies to an ungreased baking sheet; chill for 30 minutes.
Get creative! Make designs with a fork, press sprinkles into the tops, whatever! Bake until just beginning to brown around the edges, about 18 minutes. (Cookies will keep in an airtight container at room temperature about 5 days.)
Melt chocolate in microwave, 30 seconds at a time, stirring in between, then stir in oil when fully melted. Dip cooled cookies half in chocolate, or drizzle chocolate over with a spoon. (While chocolate is still warm, you can also add sprinkles, a little sea salt, chopped pistachios or pecans…there’s no limit!)
