Pour the milk into a large, heavy-bottomed non-stick pot. Heat over medium-high heat, stirring frequently, until it begins to boil.

Reduce the heat to medium-low to maintain a gentle simmer. Stir consistently to prevent a skin from forming or the bottom from scorching. Cook until the water evaporates and the milk reduces to a thick, creamy paste (similar to condensed milk).

Preheat your oven to its lowest setting, ideally between 140°F (60°C) and 150°F (65°C). If using a dehydrator, set it to 135°F (57°C).

Line a baking sheet or dehydrator tray with parchment paper or a silicone mat. Spread the milk paste in a thin, even layer across the surface.

Place the tray in the oven or dehydrator. If using an oven, prop the door open slightly with a wooden spoon to allow moisture to escape. Dry for 4 to 8 hours, checking periodically, until the paste is completely dry, brittle, and snaps easily.

Remove from the heat and let the dried milk sheet cool completely.

Break the dried milk into shards and place them into a blender, spice grinder, or food processor. Pulse until it becomes a fine powder.

Pass the powder through a fine-mesh sieve to remove any remaining large granules. Reprocess the granules if necessary.

Store in an airtight jar or container in a cool, dark place.

To reconstitute: Mix 1 part powdered milk (approx. 1/4 cup) with a small amount of cold water to form a smooth paste, then whisk in the remaining warm water (approx. 1 cup total) until dissolved.