2lbs powdered sugar (1kg)
1 tsp cream of tartar (3.5g)
6 egg whites or 6tsp/36g of meringue powder mixed with 3/4 cup water (180ml)
Combine ingredients, and whip with electric mixer for 7-10 minutes. If made in advance, cover with damp paper towels to prevent drying.
Enough for 1 house
Find it online: https://www.kitchenwrangler.com/recipes/christmas-snow-icing/