So — a Heian-period Japanese dairy preparation

Instructions

1. Clean your hands and utensils. Pour commercially heat-pasteurized whole milk into a deep frying pan or heavy pot. Store the milk as labeled and do not substitute unpasteurized raw milk. People with milk allergy must not eat this dish.
2. Warm over medium heat; when small bubbles appear at the edges, reduce to low. Use a long-handled wooden spatula to fold in the milk skin and gently scrape the bottom to prevent scorching. Do not leave the pan unattended.
3. Stir over low heat to evaporate water. About 1 hour is an untested checkpoint, not a guaranteed stage: the pan and heat change progress. Reduce heat further as it thickens, taking care to avoid hot splashes and burns from the pan.
4. Use roughly 1.5–2 hours from the start of heating as a provisional guide, aiming for a soft paste that can be gathered with the spatula, then turn off the heat. It may take longer. Time alone establishes neither doneness nor safety; do not scorch it or try to dry it completely.
5. With a clean spatula, divide into thin portions in shallow containers suitable for hot food. Do not handle the hot paste with bare hands or wait until room temperature: refrigerate promptly, targeting 4°C or below. Avoid prolonged room-temperature holding and follow container and lid instructions to prevent contamination.
6. Once thoroughly chilled, cut into pieces about 5 mm thick with a clean knife if firm enough; otherwise portion with a clean spoon. Keep refrigerated in a clean covered container and consume promptly. If anything seems abnormal or storage is uncertain, discard without tasting.