Wash the berries, remove the hulls and cut them into quarters. Heap the chopped berries in a large, non-reactive pot and add the sugar. Stir to combine.
Bundle the hibiscus blossoms in a length of cheesecloth or a large tea ball and nestle it in with the berries. Let the berries macerate at room temperature for an hour, until they are quite juicy.
Place the pot on the stove and bring the contents to a boil over high heat. Reduce the temperature to medium and simmer the strawberries uncovered for 40 to 45 minutes. They are done when the berries are very tender and the liquid has thickened.
While the berries cook, prepare a boiling water bath canner and three pint jars (six half pints are also acceptable). Wash new lids in warm, soaping water and set aside.
Remove the pot from the heat and puree the cooked berries with an immersion blender.
Funnel the finished butter into the prepared canning jars, leaving 1/2 inch headspace. Wipe the rims, apply lids and rings, and process in a boiling water bath canner for 10 minutes.
When the time is up, remove the lid from the pot and turn off the heat. Let the jars rest in the cooling water for five minutes. When that time is up, remove jars and set them on a folded kitchen towel to cool.
When the jars have cooled enough that you can comfortably handle them, check the seals. Sealed jars can be stored at room temperature for up to a year. Any unsealed jars should be refrigerated and used promptly.