Soak your nuts in filtered water for at least 4 hours.
Drain and rinse the nuts, and discard the water.
Combine all the ingredients in a blender. Your nuts-to-water ratio should be 1:2.
Blend on high for 1-2 minutes (or until the mixture has a smooth and creamy consistency).
Pour the blended mixture into a nut milk bag or a cheesecloth and place it over a container.
Gently squeeze out as much liquid as possible.
Pour 400ml of the milk and 150mg sugar into a heavy-bottomed saucepan.
Warm the mixture over low heat, stirring until the sugar is completely dissolved.
Once the sugar is dissolved, increase the heat to low/medium and bring the mixture to a gentle simmer. Avoid stirring after this point to prevent the mixture from crystallizing.
Allow the mixture to simmer for approximately 30-40 minutes, or until it has reduced by half, darkened to a deep beige color, and thickened noticeably. (Note: After about 15 minutes, the milk will start to darken and thicken.)
Once done, remove the saucepan from the heat and carefully pour the condensed milk into a jar, avoiding any crystallized sugar that may have formed around the rim. Allow it to cool completely before sealing with an airtight lid.
Store the condensed milk in a refrigerator, labeling the jar with the date.