Put the almonds in a lidded jar or bowl and pour enough water over to cover. Soak overnight (in summer, in the refrigerator).
The next day pour away the soaking water, then add approximately 1 litre of fresh cold water and process it thoroughly in a blender. It should be dense and almost smooth.
Line a sieve with muslin and pour the milk into it. Then (with clean hands!) press through as much of the residual mixture as you can.
Keep the milk refrigerated in a sealable jar or bottle for up to 3 days.