Pierce potatoes with a fork. Bake directly on the oven rack at 350F until tender, about 1 hour/ Let cool, then quarter lengthwise and scoop out the flesh, leaving a 1/4-inch shell. Brush both sides with melted butter and season with salt and pepper. Bake, skin-side up, at 450F until crisp, about 15 minutes. Puree topping ingredients together. Add topping mixture to skins and bake for 5 more minutes.