Preheat oven to 350°F. Line a baking sheet with parchment paper
Mix nut butter and sugar in a bowl until smooth
Add the egg and vanilla; stir until fully combined
Sprinkle in the baking soda and salt (if using), then fold in the dark chocolate chips
Scoop the dough into tablespoon-sized balls and place them on the baking sheet, about 2 inches apart. Flatten slightly with a fork or your fingers, they won’t spread much
Bake for 8-10 minutes, until the edges are golden but the centers are still soft
Cool on the baking sheet for 5 minutes, then transfer to a wire rack
