In a food processor, process nuts, scraping down sides once or twice during processing, until they form a thick paste, about 3 minutes. Scrape nut paste into a medium bowl.
Divide paste into 3 even portions. You only need one portion to make this recipe; you can save the rest for future batches or use it as a nut butter in other preparations. To save the extra nut paste: If the paste is thick enough to hold its shape, form the remaining portions into balls, wrap tightly in plastic and then aluminum foil, and freeze for up to 3 months; if the paste is too loose to hold its shape, transfer portions to small zipper-lock bags, press out the air, then seal and freeze for up to 3 months.
Transfer remaining portion of nut paste to a 3-quart saucepan and add 1 quart (1 liter) cold water along with the 1 teaspoon kosher salt. Set over high heat and bring to a boil, whisking to incorporate nut paste. Reduce heat to maintain a simmer and cook uncovered, stirring occasionally, until reduced by half, about 30 minutes.
