Steps

1. Bring a shallow skillet of water to a boil. Add salt to taste, a teaspoon of oil, half the garlic clove, and the chard stems. Simmer until they’re tender. (This can take as little as 4 or 5 minutes, or somewhat longer, depending on size. The best way to find out is to remove one, slice into it and take a bite.) When they’re done, set them in a colander to drain for a few minutes, then toss them with olive oil and season them with salt and pepper.
2. To make the sauce, pound the remaining half garlic clove in a mortar with ¼ teaspoon salt until mushy and smooth. Add the tahini and yogurt and work until smooth.
3. Toast the sesame seeds in a skillet over medium heat for several minutes until they begin to smell fragrant, then turn them onto a plate so they don’t burn.
4. To serve, set the stems on individual plates, add a spoonful of the sauce, the sesame seeds, and a wedge of lemon. Enjoy chilled or at room temperature.