Preheat oven to 300° and place racks in upper and lower thirds of oven. Line two large sheet pans with parchment paper. Pulse almond paste, sugar and salt in food processor until broken up, then add egg whites and puree until smooth. Transfer batter to pastry bag fitted with a 3/8-inch tip and pipe 3/4-inch rounds (1/3 inch high) about 1-inch apart in pans. Dip a fingertip in water and gently tamp down any peaks. Bake, rotating and switching position of pans halfway through, until golden and puffed, 15 to 18 minutes. (When rotating pans midway through baking, it may seem there is too much space between the cookies. Suddenly, at 15 minutes, they?ll puff up and fill that space.) Let cookies cool almost completely in their pans. Once cool, they?re much easier to cleanly remove from parchment. Make them into sandwich cookies by spreading some jam (raspberry suggested) between them or granache (3 ounces of semi-sweet chips melted with 1 to 2 tablespoons of cream, then left to thicken a bit is enough to sandwich the whole batch). Cookies can be kept in an airtight container at room temperature for a day or two, or frozen up to one month.
A bit like macaroons, these have a lot in common with them, yet they?re a lot easier to make. Makes about 4 dozen cookies, or half as much if you sandwich them.