01 -
Set your oven to 175°C first. Line up your 20 x 20 cm pan with parchment or grease it well.
02 -
Toss together the brown sugar, oats, flour, softened butter, salt, and baking soda in a medium bowl. Use your hands or a fork to mix it into little crumbly bits.
03 -
Dump rhubarb, water, cornstarch, and sugar into a pot. Stir as you heat over medium. Let it bubble for about 5–10 minutes until the rhubarb is soft and thickened up.
04 -
Take your pot off the heat and stir in the vanilla. Let it stand for 10 minutes so it can thicken and cool a bit.
05 -
Take out about 2/3 cup of crumb mix and save it. Push the rest into the bottom of the pan to make an even layer. Try not to leave any spots open.
06 -
Spread the rhubarb mixture all over the oat layer, making sure it covers every corner.
07 -
Sprinkle the crumb mix you set aside across the rhubarb so it covers most of the top.
08 -
Slide the pan into the oven. Bake 30–40 minutes until you see a golden crust on the base and the top holds together.
09 -
Let the whole thing cool off right in the pan. Once it's cool, cut it into squares and dig in.