Preheat your oven to 200 C / 400 F / gas mark 6.
Put the rhubarb, sugar, and shot of water or booze in a medium sized pot. Simmer this on low for about 10-15 minutes, or until the rhubarb is broken down.
Meanwhile, mix together the rolled oats, flour, sugar, and salt. Then rub the butter into the mixture until you get large flakes.
Pour the rhubarb into a baking dish that can hold about 1 L, then cover with the oaty, streusel topping.
Bake for about 30 minutes, or until you can see the rhubarb bubbling up around the edges and the topping is golden brown.
Serve warm with ice cream or custard.
