This seemed like a more interesting use of rhubarb than a fruit+rhubarb pie or tart, and I’ve been meaning to try rhubarb and rosemary in some combination since I heard it was a worthwhile duo. I’ve never made gelatin from scratch (except classic Jell-O) so don’t be intimidated by the seemingly complex chemistry.
Gelatin requires a few things to successfully set: gelatin powder, cold liquid and hot liquid. Since you can’t really buy rhubarb juice you’ll have to make it, and here is the opportunity to flavor it with anything you want. I added rosemary and some lemon juice but you could really do any spices/fruits you’d like.
1/2 ounce gelatin (2 packets)
1/2 cup cold water
~2 pounds rhubarb, cleaned and roughly chopped (8-10 stalks, NOT peeled)
Pinch of salt
1 cup sugar
Juice of 1 lemon
1 tablespoon roughly chopped rosemary
Combine the gelatin and water, it’ll make a slushy gel (that’s what you want). Keep it in the fridge until the rest of the gelatin mixture is ready.
Combine all the other ingredients in a saucepan and cook over medium-high heat, stirring as the rhubarb reduces and the liquid begins to boil. All the cooking will take about 20 minutes, but after 10-15 when the rhubarb is breaking apart you could mash the mixture a little to separate the liquid from the rhubarb chunks. As it all begins to combine, taste the mix for sweetness and rosemary flavor.
Once the mix is sufficiently liquid and the remaining pieces of rhubarb are minimally intact, strain the juice through a strainer (it’ll be beautifully pink and you won’t get much usable juice, this is normal). Be patient. If the mix is no longer very hot (like almost boiling) put it back on the stove for a minute until simmering.
In a bowl combine the gelatin mix you refrigerated earlier with the juice (you should have about three cups, add a little hot water if you need to) and stir to combine. Spoon this into glasses or a tray of some sort, the presentation is up to you, and carefully put it in the refrigerator. Wait as long as you can without touching or jiggling your gelatin (at least 3 hours), and if you’ve done everything according to plan the result will be firm, cold, delicious and of course rhubarb-y.