Preheat the oven to 180° Celsius

Butter an oven proof dish (or ramekins)

Cut the rhubarb into 1 inch batons

Toss with the cinnamon sugar

Place into your oven proof dish

Mix the flour and the butter with your finger tips until the flour resembles bread crumbs

Add the cinnamon sugar, nuts and oats and mix with a fork

Top the rhubarb with the crumble, being very generous

Bake for 25 minutes