In a separate small bowl, whisk together almond flour, cocoa powder, salt, and espresso powder (if using) until no lumps remain.
Sift the dry mixture over the chocolate-egg mixture using a fine-mesh sieve. This prevents clumping and ensures no grit.
Using a flexible silicone spatula, gently fold the dry ingredients into the wet mixture. Use a 'J' motion—scrape the bottom, lift up and over.
Fold just until no dry streaks remain (about 15-20 strokes). You should still see some streaks of cocoa—they'll incorporate during baking.
If making chocolate chip gluten free brownies, fold in the chocolate chips now with just 3-4 gentle strokes.