Mix dry ingredients – In a large bowl, whisk together flour, baking soda, salt, brown sugar, and granulated sugar.
Incorporate butter and milk – Add softened vegan butter and plant-based milk. Mix with a spoon or stand mixer. If mixing by hand, dough may seem dry—keep stirring until it comes together.
Form dough – Shape into one large ball, then break into smaller portions and roll into cookie dough balls.
Chill – Cover and refrigerate for at least 1 hour (overnight is best) for thicker cookies.
Bake – Preheat oven to 350°F (175°C). Arrange dough balls on a parchment-lined baking sheet and bake for 15 minutes on the center rack
Cool & serve – Let cookies rest on the sheet for 5 minutes before transferring to a wire rack. Enjoy warm for maximum gooeyness.