Make the flax egg: In a small bowl, mix ground flaxseed and water. Let it sit for 5–10 minutes until thickened and gel-like.

Cream the butter and sugars: In a medium bowl, beat vegan butter with brown sugar and granulated sugar until light and fluffy, about 1–2 minutes. Stir in vanilla.

Add flax egg: Mix the thickened flax mixture into the butter-sugar base until fully combined.

Combine dry ingredients: In a separate bowl, whisk flour, baking soda, and salt. Add to the wet ingredients and stir until a soft dough forms. Do not overmix.

Fold in mix-ins: Stir in chocolate chips and nuts, if using. The dough should be scoopable and slightly firm.

Chill briefly (recommended): Refrigerate the dough for 15–20 minutes. This helps prevent spreading and improves texture.

Prep the air fryer: Preheat your air fryer to 320°F (160°C) for 3–5 minutes. Line the basket or tray with parchment cut to fit, or use perforated parchment. Avoid letting parchment touch the heating element.

Portion the dough: Scoop 1.5–2 tablespoons of dough per cookie and roll into balls. Place 2 inches apart in the air fryer basket. Lightly press to flatten the tops just a bit.

Air fry: Cook at 320°F (160°C) for 6–8 minutes. Start checking at 6 minutes. The edges should look set and lightly golden; centers may look slightly soft—that’s perfect.

Rest to set: Let cookies cool in the basket for 3–5 minutes, then transfer to a rack to finish setting. They firm up as they cool.

Repeat: Bake additional batches as needed. If the basket gets hot, give it a minute between rounds to avoid over-browning.

Optional finishing touch: Sprinkle warm cookies with a pinch of flaky sea salt.