Step 1

Make the cookie layer: Preheat the oven to 375°F (190°C). Grease 10-inch square baking dish nonstick spray, line with parchment paper, then spray again.

Step 2

In a large bowl, combine the vanilla cake mix, egg yolk, and oil and mix until the dough comes together. Press the cookie dough into the prepared pan in a flat, even layer, then poke holes all over the surface.

Step 3

Bake the cookie layer for 15–20 minutes, or until golden brown. Remove from the oven and let cool completely, about 20 minutes.

Step 4

Make the caramel layer: In a medium pot, combine the butter, brown sugar, sweetened condensed milk, corn syrup, vanilla, and salt. Cook over medium-low heat, stirring frequently, for 5–8 minutes until the sugar dissolves. While stirring constantly, increase the heat to medium-high and bring to a boil, then continue cooking until the caramel has thickened, about 6 minutes.

Step 5

Pour the caramel over the cookie layer, then refrigerate until slightly solid, about 30 minutes.

Step 6

Make the chocolate layer: In a medium, microwave-safe bowl, combine the dark chocolate and coconut oil, then microwave in 30-second intervals, stirring between, until completely melted and smooth.

Step 7

Pour the chocolate over the caramel layer and sprinkle with flaky sea salt. Refrigerate for about 20 minutes, or until the chocolate has hardened.

Step 8

Use the parchment to lift the cookie from the pan, then cut into 50 1 x 2-inch bars.

Step 9

Refrigerate in an airtight container until ready to serve, up to 3 days.

Step 10

Enjoy!