Pulse 12 oz fresh cranberriesin a food processor 10 to 15 times, until finely chopped but not mushy. They should look like coarse relish.
Place 1 can (20 oz) crushed pineapple in a mesh strainer set over a bowl. Drain the pineapple, pressing on it gently with a spatula to remove most of the juice.
Place the cranberries in a large non-metal bowl, stir in ¾ cup granulated sugar, drained pineapple, and a Pinch of salt. Cover, and refrigerate at least 3 hours, or overnight.
After letting the mixture rest in the fridge, place it in a mesh strainer and let the extra juice drip out for a few minutes. If you skip this, the fluff will be watery. Save the juice for punch or spritzers.
Stir 1½ cups mini marshmallows and ½ cup chopped walnuts into the cranberry mixture.
Beat 1 cup heavy whipping cream to medium-stiff peaks, then gently fold it into the fruit mixture.
Refrigerate until ready to serve. It keeps nicely in the fridge for several days and can be made a day ahead.
Notes
Variations: several of the old recipes called for a diced apple, a sliced banana, or a cup of halved grapes. If you'd like more fruit/crunch, give one or more of those a try!Whipped topping: you can replace the whipped cream with 2 cups of Cool Whip. If you choose this route, reduce the sugar in the recipe by half.Leftovers: the salad will keep for a handful of days in the fridge, tightly covered.Why use a non-metal bowl? The cranberries and pineapple are acidic and can react with some metal bowls, which can give the salad an off taste. A glass or ceramic bowl works best.