Cup of Yum
1. Preheat your oven to 180°C/350°F (or 160°C/320°F for fan or convection ovens) and line an 8x10-inch tin with baking paper. (note 1)
2. Add the softened butter to a bowl with the caster sugar and brown sugar. Mix to make a thick paste, using an electric whisk or stand mixer to assist if required.
3. Add the egg and vanilla extract and mix well until smooth.
4. Add all of the self-raising flour and mix it in. When it starts to come together, use your hands to press it into a ball of dough. (note 2)
5. Add the mini peanut butter cups and the chocolate chips, saving a few for the topping.
6. Take ¾ of the cookie dough and press it into the bottom of your lined tin. Set the rest aside to use as the topping later.

Fudge layer:

Cup of Yum
1. Break the chocolate into pieces and place it into a saucepan with the condensed milk. Place over low heat on the stove and stir gently until the chocolate has fully melted.
2. Pour the chocolate fudge mixture over the cookie dough in the tin and spread it out evenly. Work quickly as it'll start setting as soon as you remove it from the heat.
3. Divide the remaining cookie dough into 4 pieces and use your hands to flatten each piece as much as you can. Place the pieces over the fudge then use a toothpick to swirl them together. (see video if you're unsure)
4. Top the cookie with extra mini peanut butter cups and chocolate chips.
5. Bake for 22-25 minutes, until golden brown all over and slightly pulling away from the edges. (note 3)
6. Leave it in the tin to cool completely then pop it in the fridge for 2-3 hours to set.
7. Once set, remove the cookie from the tin, cut it into slices and enjoy!