This is the creamiest mashed potato ever. I only ever use skim milk.
Substituting heavy cream with skim milk fundamentally alters the emulsion mechanics of this dish, shifting the reliance for mouthfeel from milk fat to pure starch gelatinization. Dairy proteins in the milk interact with the released starches, requiring precise temperature control to avoid breaking the delicate liquid-solid suspension. Starch cells rupture when cooked, releasing amylose into the surrounding liquid; boiling potatoes in milk introduces sugars and proteins that coat these starch molecules, preventing them from rebonding into a rigid, gluey mass.
Undercooked cubes will stubbornly resist mechanical breakdown, guaranteeing a pasty, gummy texture because the internal starch has not fully hydrated. Visual cues dictate donateness: pieces must crumble apart at the edges before any agitation occurs. Cutting tubers uniformly into two-centimeter cubes ensures heat penetrates the center at the exact rate the exterior softens, avoiding the hazard of overcooked outer layers while the core remains firm.
Mechanical mashing requires exact physical parameters to incorporate butter without overworking the mixture. Inserting a butterfly attachment keeps blade shear forces low, distributing fats evenly without tearing starch chains into a sticky paste. Processing for twenty to thirty seconds at a moderate speed introduces enough air to lighten the density while preserving the structural integrity of the individual potato cells.