Preheat the oven to 180C/160C fan, and line 2-3 large baking trays with parchment paper.
In a bowl, whisk together the plain flour, bicarbonate of soda, salt, and cornflour. This just distributes all the ingredients evenly.
Melt your butter carefully and then add to a bowl. Add the two sugars. Whisk for two minutes with an electric whisk (or three minutes by hand)
Add in the egg and vanilla, and whisk again briefly to combine.
Add in the dry ingredients and the chocolate chips, and beat until a cookie dough is formed.
Add in the Rolos and combine the mixes - don't use an electric mixer for this bit as you don't want to break the Rolos up too much.
Using a 5-6cm ice cream/cupcake/cookie scoop, scoop your mixture. The mixture can be larger than the scoop, but it gives you a general idea of how to make them consistently sized.
I made 15 cookies out of mine, as I made them quite large. If there are any leftover chocolate chips or Rolos at the bottom of the bowl, press them into the top.
You want to make sure there is only about 6 cookies for a 40cm long tray for example, so that when they spread in baking, they don't touch.
Bake the cookies in the oven for 12-14 minutes, and then leave to cool on the tray for 15 minutes before transferring to a wire rack. Enjoy!
Notes
I didn't freeze my Rolos as I wanted the caramel to ooze. If you don't want it to ooze as much, its best to freeze the Rolos overnight so that they are solid.
Be careful when these comes out of the oven as the caramel will be VERY HOT.
These cookies will last up to five days, if not eaten already.
I used chocolate chips rather than chunks of a chocolate bar for the other chocolate in the cookies so that there was better distribution of chocolate for each bite!