The water is in there to make sure it doesn’t get too hot when infusing the butter, then I strain out the weed, freeze the butter/water mix.
The butter floats to the top, and a lot of the undesirables like some of the chlorophyll come out in the water. Toss the water, save the butter.
Let solidify again.
Then, I’ll melt the green butter with some more fresh water to “wash” it. It helps pull undesirable taste and more chlorophyll out of the butter. Then freeze again, toss water, and repeat. I usually wash my butter three times to get rid of some of that nasty taste.