Measure the olive oil into a stainless steel pot or plastic bowl. Be sure that it's large enough to hold the whole recipe with room to mix with a stick blender.

Heat the oil to 105 degrees and set aside.

Measure the distilled water and lye into SEPARATE heat proof non-reactive bowls. Add the lye to the water a tablespoon at a time (never add the water to the lye!). Stir until the lye is fully dissolved.

Add the sodium lactate into the lye water (if using).

Allow the lye water mixture to cool until it's about 105 degrees.

Pour the lye mixture into the warmed olive oil mixture. Insert the stick blender and blend to a light trace.

Add breastmilk and stir to combine.

Pour the soap into a 10'' loaf mold.

Optional - Use a small spray bottle to spray the top of the soap with rubbing alcohol a few times over the next 90 minutes. This will help prevent soda ash forming on the surface. It's cosmetic, and harmless, but the soap looks better without it.

Allow the soap to cure in the mold for 2 to 5 days. Un-mold the soap and cut it into bars.

Allow the bars to cure for at least 6 weeks before using. They'll still be a bit soft at this point, and allowing 3 months before using will result in a firmer bar.