First, stir the ground flaxseed into the water in a small cup and leave it for 10 minutes, until it thickens and turns slightly slippery.

Next, beat the softened vegan butter and the dark brown sugar together with a spatula for a full minute, until the mixture looks like wet sand rather than two separate things. Stir in the flax mixture, the oat milk and the vanilla until the bowl looks smooth instead of curdled.

Then add the flour, salt, oats, baking soda and cinnamon and fold just until no dry flour is left. Fold in the chocolate chips last, stopping while the dough still looks slightly streaky.

After that, cover the bowl and refrigerate for at least 30 minutes and up to 2 days. This is not optional: vegan butter is soft and wet, and unchilled dough spreads into thin greasy discs.

Heat the oven to 350 degrees Fahrenheit and line two light-colored baking sheets with parchment. Roll the dough into 15 balls of about 55 g each, flatten each one slightly with your palm and space them three inches apart.

Bake for 11 to 13 minutes, until the edges are set and slightly darker and the middles still look damp and underdone. Rap the sheet flat on the counter as it comes out, which drops the puffed centers and gives the cookies their ripple.

Finally, scatter a little flaky salt over the tops and leave the cookies on the hot sheet for 5 minutes before moving them, since they are fragile until the fat firms up. Cool the sheets between batches so the next tray does not spread.