I found this at an "all natural" site...still doesn't say how to extract powder or which "mallow plant" to use. Good luck with your search!

Marshmallows Treats

Make your children a natural treat without all the chemicals, coloring
and preservatives which make our children hyperactive.

2 egg whites
1 tsp vanilla
1/2 cup raw cane sugar
1 tbsp powdered Marshmallow (root)

Whip egg whites until almost stiff. Add vanilla and whip until stiff. Then whip in the sugar, 1 tsp at the time. Finally, add Marshmallow and whip again. Place by teaspoonfull on cookie sheet. Bake in 325 oven for 1 hour.