• Pre-heat the oven to 180 C / 350 F.
• Line an 8-inch square tin with baking paper, making sure you cover the sides.
  

For the Peanut Butter Layer

• Add the sugar to the Thermomix bowl. Mill for 10 seconds / speed 9. Set aside.
• Add the peanut butter and butter to the bowl. Melt for 3 minutes / 90 degrees / speed 2.
• Add vanilla extract and sugar. Mix for 30 seconds / speed 5. Set mixture aside.

For the brownie mixture

• Break up the chocolate into pieces and place in the Thermomix bowl. Cut the butter into cubes and add to the Thermomix bowl.
• Melt the chocolate and butter for 4 minutes / 50 degrees / speed 2. Check that the chocolate is melted. If not repeat for a further 2 minutes.
• Add sugar to the bowl. Mix 10 seconds / speed 4.
• Add eggs and vanilla extract to the bowl. Mix 5 seconds / speed 4.
• Add flour and cocoa powder to the bowl. Mix 30 seconds / speed 4.
• Add chocolate chips to the bowl. Mix on REVERSE / 10 seconds / speed 4.

Assembling the peanut butter brownie

• Lightly cover your kitchen surface with icing sugar. Turn out the peanut butter mixture and roll out to roughly the size of your baking tin.
• Smooth half the brownie mixture into the prepared baking tin. It should be thick and fudgy.
• Carefully lay the peanut butter layer over the brownie mixture. You may need to do this in sections. Don't worry if it looks messy, you will be covering it up.
• Cover the peanut butter layer with the remaining brownie mixture and smooth over the top.
• Bake in the oven at 180 C / 350F for 25 minutes.
• Allow to cool in the tin before cutting into squares and serving.