Make yogurt with milk and store-bought yogurt as starter

Heat 1 quart of whole milk to 180°F (82°C), then cool to 110°F (43°C). Whisk in 2 tablespoons of plain yogurt with live active cultures. Pour into a clean jar, cover, and keep warm (105-115°F) for 6-12 hours. The longer it incubates, the tangier it gets. Refrigerate when set.

Why It Works

Heating milk denatures the proteins so they form a smooth gel instead of separating. The yogurt starter introduces beneficial bacteria (Lactobacillus, Streptococcus thermophilus) that ferment the lactose into lactic acid, thickening and souring the milk.

Tips

• Use plain yogurt with "live active cultures" on the label as your starter
• Keep warm in an oven with just the light on, a cooler with a jar of hot water, or wrapped in towels
• Save 2 tbsp from each batch to start the next one — endless yogurt from one purchase
• For thicker Greek-style yogurt, strain through cheesecloth for 2-4 hours after refrigerating