Toss the rhubarb with the sugar, ginger, and cornstarch.
Divide it evenly between four individual baking cups.
Put the crumble ingredients in the same bowl and mix with your fingertips until it has a coarse crumbly consistency.
Sprinkle the topping over the rhubarb. Set the cups on a baking tray (to catch any drips) and bake for about 25-30 minutes ~ if everything's bubbling and just starting to turn golden on top, you're good to go.
Serve warm with whipped cream or ice cream.
You can bake the crisp in a 9 inch baking pan or pie plate as well. The baking time should be about the same.