Preheat the oven to 180°C (160°C fan). Line an 8-inch square tin with parchment paper.
Make the crumble: Combine the oats, sugar and vanilla. Rub in the butter until the mixture resembles coarse crumbs. Spread onto a lined baking tray and bake for 15–20 minutes, stirring halfway, until golden. Leave to cool.
Make the base: Melt together the peanut butter, coconut oil and honey in a saucepan or microwave. Stir in the oats and cocoa powder. Press firmly into the lined tin.
Make the topping: Melt the chocolate and coconut oil until smooth. Stir through the vanilla and pour over the base.
Sprinkle over the cooled crumble, gently pressing it into the chocolate.
Chill for 1–2 hours until set.
Slice into 16 squares and enjoy!
