Place all the filling ingredients in a sauce pan and bring to a boil. Immediately reduce heat to a simmer.
Continue to simmer for approximately 1 hour. The starch should be completely dissolved and you should have a somewhat thick (almost like stew), stringy substance when done. Stir frequently.
While the rhubarb cooks, place all the topping ingredients into a food processor and blend until well combined. It should stick together just slightly, but you should still be able to "sprinkle" it over the filling.
Preheat oven to 350 degrees F.
Pour the rhubarb into a lasagna dish or other baking pan. Mine was 9x13. This should be a thin layer.
Sprinkle with the topping so the entire thing is evenly covered. Place in oven and bake for 30 minutes. The topping should have a nice, golden appearance. Check frequently after the first 20 minutes to ensure nothing gets burned.
Allow to cool completely so that the bottom of the pan can be held in your had. In other words, not hot at all. Place the entire dish in the freezer and freeze for about 2 hours. The idea here is to CHILL it, not freeze it. Once it's frozen, it's very hard to cut. So if you accidentally freeze it, just let it sit out on the counter until it's soft again.
Slice into 15 pieces and serve.
Storage: Keep in the fridge for up to 6 days.
Notes
Please note that the nutrition data is a ballpark figure. Exact data is not possible.