70g(⅓cups)chocolate chips(optional, milk, white or a mix)
Pre-heat oven: 160°C (fan) / 180°C / Gas Mark 4 / 350 F
Cream together the butter and sugars until fully combined.
Add in the egg and vanilla, beating the mix until smooth.
Sift in the flour and salt, stirring together until just combined.
Mix in the chocolate chips.
Pop your cookie dough into the fridge while you make the brownie mix.
Melt the butter and dark chocolate, either in the microwave (no more than 30secs at a time) or over a double boiler, stirring until completely melted and smooth.
Using an electric mixer, whisk the eggs and sugar. This should whip up to being thick and creamy like a milkshake, and can take roughly 3-8mins.
Pour the cooled chocolate mix over the fluffy eggy mix, then gently fold together with a spatula or wooden spoon.
Sieve and fold the plain flour and cocoa powder into the eggy chocolate mix, until just combined.
Stir in the chocolate chips (if using) until they’re dotted throughout.
Line a 9in x 13in baking tin with grease-proof paper. Squish the cookie dough down into the bottom of the tin firmly, either using your hands or the back of a large spoon. You want a thin and even layer across the base of the tin.
Layer the Oreos on top - as many as you can fit with no overlaps and leaving a half inch of space at the edges.
Pour the brownie mix over the Oreo layer, covering them completely and smoothing over top.
Bake for 35 - 40mins. Once it's cooked, a skewer should come out clean from the brownie layer and the surface should be lightly cracked and papery. The brownies shouldn’t wobble like a liquid once cooked.
Allow to cool completely and then cut into squares.