Cut 4 sweet potatoes into wedges; toss with olive oil, salt and pepper on a baking sheet. Bake at 425 degrees F, flipping once, until browned, 20 to 25 minutes. Mix 3 tablespoons softened butter with 1 tablespoon harissa (or other chile paste), 1 grated garlic clove, the zest of 1 lime and a pinch of salt. Toss with the potatoes and some chopped chives. Season with salt. Serve with lime wedges.