Remove the stems from the chard. Trim the ends of the stems then thinly slice. Chop the chard into largish pieces.

Heat 5 tablespoonss oil in a large frying pan over medium-high heat. Add 1 chopped onion and season with 2 teaspoons kosher salt and 1/2 teaspoon pepper. Cook, stirring occasionally, until translucent.

Lower heat to medium and add 2 pounds diced new potatoes and cook, stirring occasionally, until golden. Add 1 clove minced garlic and cook a minute more. Add the chard stems and leaves a little at a time. It will shrink as it cooks, keep stirring and adding handfuls of chard. Once chard is tender, about 3 minutes, add 1/4 teaspoon chile flakes and season with salt and pepper.

Fill warm tortillas with potato-chard mixture, top with a bit of sour cream or a crumbling of queso fresco, if you'd like (or leave it off if you want to keep these tacos vegan) and a spoonful of your favorite salsa.