Everyone adores this slice and with good reason – it’s completely delicious but thanks to the crumbly oat layers, kind of feels a smidge healthy!
Preheat oven to 180C and grease and line a 20x20cm slice tin.
Place the butter, brown sugar and vanilla in the bowl of an electric mixer with paddle attachment and cream until pale and fluffy.
Add remaining ingredients and beat for 30 seconds or just until well combined.
Press half into the base of your tin, pop the rest in the fridge and then the tin in the oven for 15 minutes or until pale golden.
Meanwhile make the filling; combine all ingredients in a small saucepan over medium heat and stir, until well combined.
Pour the caramel over the par-baked base then crumble over reamining oat mixture. Return to the oven for another 15-20 minutes or until the crumble looks golden brown.
Once completely cool, slice into squares and keep in the fridge if you live somewhere hot!! I also find it easiest to slice this after it's been in the fridge for a while which gives the caramel a chance to really set.