Prepare the brownie layer. In a medium mixing bowl, combine the oat flour, maple syrup, cocoa powder, peanut butter, vanilla extract, and sea salt. Mix until a thick, fudgy dough forms. If the mixture is too wet or sticky, gradually add more oat flour, 1 tablespoon at a time, until it is firm enough to press into a pan. Line an 8 × 8-inch baking pan with parchment paper and press the brownie mixture evenly into the bottom.

Make the cookie dough layer. In a separate bowl, combine the peanut butter, maple syrup, vanilla extract, oat flour, and sea salt. Mix until a soft cookie dough forms. If the dough is too dry, add dairy-free milk, 1 tablespoon at a time, until it reaches a soft, spreadable consistency. Fold in the mini chocolate chips.

Assemble the brookies. Transfer the cookie dough mixture over the brownie layer or just interchange pieces and press together!

Prepare the optional chocolate shell. Melt the unsweetened chocolate chips with the coconut oil or avocado oil in a microwave-safe bowl in 20-second increments, stirring between each until smooth. Pour the melted chocolate over the cookie dough layer and spread evenly. Sprinkle with flaky sea salt if desired.

Freeze to set. Place the pan in the freezer for 45–60 minutes, or until the brookies are completely firm and the chocolate shell has hardened.

Slice and enjoy. Remove the brookies from the freezer and let them sit at room temperature for 5–10 minutes to soften slightly. Lift them out of the pan using the parchment paper and slice into 8 large or 10 smaller brookies with a sharp knife.

Store the brookies in an airtight container in the refrigerator for up to 1 week or in the freezer for up to 2 months. For the best fudgy texture, allow frozen brookies to sit at room temperature for a few minutes before enjoying.