Preheat oven to 350 ℉ (175 ℃). Line a 9 inch (23 cm) square baking pan with parchment for easier clean up. Set aside.
In a large bowl, toss the rhubarb, sugar, cornstarch, ginger, vanilla and cinnamon until rhubarb is well coated. Scrape the mixture into the prepared baking pan.
In the same bowl (no need to wipe it out!), mix together the oats, hemp hearts, walnuts, oil, sugar, vanilla and cinnamon until well combined.
Sprinkle the crisp topping evenly over the fruit mixture. Place the pan in the oven and bake for 45-55 minutes, until the crisp topping is golden and the fruit mixture is bubbling and thick.
Let cool for at least 10 minutes before serving. You can serve warm, room temperature or cold!
