First, positively identify comfrey (Symphytum officinale), which is a perennial that grows to about three feet tall in moist grasslands and farm lands. Comfrey has lanceolate leaves that are fuzzy and resemble mullein; but unlike mullein, comfrey has bell-shaped purple or whitish flowers. Use a field guide if in doubt. Dry the leaves in a dehydrator if you need the salve soon, or just dry them indoors for a few weeks if you are making salve for the season. Melt one cup of Crisco or lard in a crock pot (try to get it around 150 degrees). Then add in one cup of crushed, dried comfrey leaves and let it soak for 3 hours at 150 degrees. Next, strain the solid leaf bits out by pouring the mixture through a strainer, and store the green-colored salve in the fridge up to one year.