Line an 8 x 8-inch pan with parchment paper and set aside.

In a mixing bowl, combine 1 1/2 cups oat flour and 1 cup vanilla protein powder; whisk briefly to blend and set aside.

In a microwave-safe bowl or in a small saucepan over low heat, combine 2 cups peanut butter and 1/2 cup brown rice syrup. Warm just until the mixture is smooth and pourable, stirring to combine (microwave in 20–30 second intervals, stirring between intervals, or heat gently on the stovetop).

Pour the warm peanut butter–syrup mixture into the dry ingredients. Stir thoroughly until the dry ingredients are fully incorporated and the mixture is uniform. The mixture will be thick; keep stirring and scraping the bowl sides to incorporate everything.

Transfer the mixture to the prepared pan. Use a spatula or the back of a spoon to press it firmly and evenly into the pan so the surface is compact.

Refrigerate the pan for at least 20 minutes to firm up.

While the mixture chills, place 1/3 cup chocolate chips and 1 teaspoon coconut oil in a small microwave-safe bowl or in a heatproof bowl set over a saucepan of simmering water. Heat and stir until the chocolate and oil are fully melted and smooth.

Remove the pan from the refrigerator and pour or drizzle the melted chocolate over the top. Spread or smooth as desired.

Return the pan to the refrigerator and chill until the chocolate topping is set. Once set, lift the parchment out of the pan and cut into squares.