Preheat the oven to 450 degrees. Melt butter with olive oil. Roll the diced potatoes in the hot olive oil and butter mixture before shaking them in the onion mix. That will help make the mix stick to the potatoes during baking. In a 13 x 9-inch baking or roasting pan, arrange the potatoes so that none touch each other. Bake, uncovered, stirring occasionally, 40 minutes, or until the potatoes are tender and golden brown. Substitute garlic mushroom mix, onion-mushroom mix, golden onion mix, savory herb with garlic or fiesta herb with pepper soup mix.