Take the 1 1/2 pounds of rhubarb and wash it thoroughly. Trim the ends and cut the stalks into 1/2-inch pieces. Place the pieces in a medium sauce pan and cover them with the 2 1/2 cups of water. The water might not cover all of the rhubarb and that's okay. When you are cooking it, it will break down. Cook the rhubarb for 15 minutes over a medium heat until the veggie has turned all mushy and gross.
Let the mixture cool and then strain out the pulp so that all you are left with is this beautiful pink juice. Gorgeous, right? I just want to dive right in.
Now make the syrup. Using a very small saucepan, combine 3/4 cup of sugar, the 1 cup of remaining water, 1 cinnamon sticks, 2 Chile de árbols, and 4 cloves. Bring to a simmer over a medium-high heat then cover, remove from stove and let it steep for 15 minutes. Oh, and the below photo is of a double batch, if you are wondering why there are more ingredients than listed.
Strain the syrup and combine it with the 2 1/2 cups of rhubarb juice. Divide it amongst the popsicle mold and freeze it for about 10 hours.