Melt butter in a medium saucepan over low heat. Once melted, add brown sugar, almond flour, salt, and corn syrup (or milk). Cook, whisking constantly until sugar dissolves and ingredients are fully combined—about 3–4 minutes. If ingredients separate, remove from heat and whisk vigorously until they come back together.

Remove from heat and stir in vanilla. Mixture will be grainy and shiny. Let it rest 5–10 minutes to thicken as the oven preheats.

Preheat oven to 350 °F (177 °C). Line 2–3 baking sheets with parchment paper or silicone mats.

Drop scant teaspoons of the mixture (about 1 tsp each) onto prepared sheets, spacing them at least 3 inches apart to allow for spreading.

Bake for 6–8 minutes until edges are golden and centers bubble and sizzle. The cookies will spread dramatically in the oven.

Let cookies cool on the baking sheet for 5 minutes to crisp up, then transfer to a wire rack to cool completely.

(Optional) Once cool, sandwich cookies with Nutella or melted chocolate. Use 1–2 teaspoons per pair. Alternatively, drizzle or dip them in chocolate.

Store cookies without filling in an airtight container at room temperature up to 1 week; with chocolate or Nutella filling, they’ll stay fresh for about 3 days at room temperature or up to 1 week refrigerated.