I found this recipe on the side of a bag of whole red potatoes
A list of ingredients never warns you about the moisture trapped inside thick-skinned red potatoes or the way wet coatings tend to scorch before the interior finishes softening. Mustard contains water and solids that burn easily at 400 degrees Fahrenheit, meaning the heat must be managed carefully so the spices bloom rather than char. Pricking the skins with a fork creates essential steam vents that prevent the potatoes from splitting open violently under high heat. Spacing the tubers apart in the roasting pan rather than crowding them allows dry oven air to circulate, which is the only way to achieve a proper exterior roast instead of a steamed texture. Judging doneness without a thermometer requires a metal skewer or a sharp paring knife inserted into the absolute center of the largest potato. Resistance means the starch molecules have not fully gelatinized, whereas a smooth, effortless slide indicates the interior is completely tender. Whole red potatoes share roots in American home-style roasting traditions where convenience products meet basic pantry spices to create robust side dishes. Roasting times can stretch from 45 to 60 minutes depending on the exact moisture content of the tubers and the thermal mass of the roasting pan.