Mix water, sugars, and molasses in saucepan. Bring to boil.
2 c. brown sugar, 1 1/2 c. white sugar, 2/3 c. molasses, 2 c. water
Boil on medium heat for about 2 - 3 minutes.
Cool completely.
Add peanut butter and marshmallow cream and mix well, until smooth and creamy.
2 1/2 lb. peanut butter, 1 1/2 c. marshmallow cream
Serve on bread or buns. Or anything else you like peanut butter with.
Store in an airtight container in a cool place.
Notes
You can use any kind of molasses or Karo for this recipe. It just depends on how well you like that robust molasses flavor. Blackstrap molasses has a very strong and distinct flavor that some people do not like. I would personally recommend using light-tasting molasses. And if you're not a molasses person, feel free to use light Karo. If you just want to try the recipe and don't want to make a lot, go ahead and halve the recipe.