Combine rice with 1 cup of plant-based milk in a sauce pan, cover and bring to a boil over high heat. Once boiling reduce to low and continue to cook until rice is cooked and all plant-based milk has been absorbed. Meanwhile whisk remaining 1 cup of plant-based milk with cornstarch until well combined.
Once rice is cooked, stir in plant-based milk/cornstarch mixture and raisins. Bring to a boil over high heat and reduce to medium once boiling. Allow the pudding to thicken up, stirring occasionally. Add sweetener here if desired (brown sugar, agave, pure maple syrup--I find the raisins make it sweet enough, esp. with sweetened non-dairy milk, but most traditional recipes call for sugar). If the pudding becomes too thick, thin out with non-dairy milk.
If it's not thick enough, continue to cook. Once thick and creamy (takes 3-5 mins) stir in cinnamon as desired (I like 1/4 to 1/2 tsp). Allow pudding to completely cool then transfer to fridge in an air-tight container. Chill for several hours before serving. If you find your pudding didn't turn out sweet enough, drizzle a little pure maple syrup over top.