Prep the pan: Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving overhangs for easy lifting. Lightly grease the paper.

Melt and mix: In a large bowl, whisk the melted butter with the sweetener until combined and glossy. If the mixture seems thick or gritty, keep whisking for 30 seconds more.

Add eggs and vanilla: Whisk in the eggs one at a time, then add vanilla. Mix until smooth and slightly thickened. This helps create a shiny, fudgy top.

Stir in dry ingredients: Sift or whisk together almond flour, cocoa powder, coconut flour, baking powder, and salt. Add to the bowl and fold gently until no dry spots remain.

Adjust consistency: The batter should be thick but spreadable. If it looks too stiff, mix in 2–3 tablespoons almond milk, 1 tablespoon at a time. Fold in chocolate chips if using.

Spread the batter: Transfer batter to the prepared pan and smooth the top with a spatula.

Peanut butter swirl: Warm the peanut butter slightly if it’s very thick. Dollop 8–10 teaspoons over the batter. Use a butter knife to gently swirl, dragging through in S-shapes without overmixing.

Bake: Bake for 18–22 minutes. Start checking at 18 minutes. The center should be just set with a few moist crumbs on a toothpick. Do not overbake.

Cool and finish: Let brownies cool in the pan for at least 20–30 minutes to set. Sprinkle with a pinch of flaky salt if desired. Lift out using parchment and slice into 12 squares with a sharp knife.

Serve: Enjoy warm for extra fudginess, or chill for cleaner cuts and a denser texture.