Prep the pan – Lightly grease, then line with criss-cross parchment, leaving overhang for easy lift-out.
Melt the fat – Gently melt ½ cup (115 g) butter or refined coconut oil until just liquid; set aside to cool 2 min.
Combine sweeteners – In a small bowl whisk ¾ cup monk-fruit/erythritol blend with ¼ cup allulose (optional) to break lumps.
Whip eggs & vanilla – In a separate bowl beat 2 large room-temp eggs + 1 tsp vanilla for 1 minute until lighter in colour.
Stream in sweetener – While whisking, sprinkle the sweetener mix into the eggs and whip 30 sec more until glossy ribbons form.
Fold in melted fat – Drizzle cooled butter/oil down the bowl’s side; switch to a spatula and fold until no streaks remain.
Add dry ingredients – Sift together ½ cup almond flour, ⅔ cup Dutch cocoa, ½ tsp baking powder, ¼ tsp sea salt; fold into wet batter in two additions.
Finish with extras – Stir in ⅓ cup sugar-free dark chocolate chips and, if desired, 1 tsp instant espresso powder for flavour balance.
Bake 18–22 min – Spread batter evenly, tap pan once, bake until a toothpick 2 cm from the edge shows moist crumbs.
Cool & portion – Place pan on a rack, cool 20 min, then lift and slice 4 × 4.
