Preheat the oven to 180C/350F/Gas 4. Line an 8x8-inch square baking pan with foil or parchment paper, and set aside.
Place the butter, sugar, cocoa powder, and salt into a microwave-safe bowl. Heat for 1 minute, then stir to combine. Heat for another minute until the mixture is very warm/hot to the touch.
Mix in the eggs and vanilla until fully combined, then fold in the flour. Fold in the chocolate chips, being sure not to let them fully melt into the batter.
Spoon half of the batter into the prepared pan and spread out evenly.
For the Nutty Caramel Centre
Place the caramels and milk in a microwave-safe bowl, and heat in 30 second intervals, stirring after each one, until melted and smooth. Allow to cool slightly and thicken up in the fridge - about 20 - 30 minutes.
Fold in the peanuts. Spread the caramel evenly over the brownie batter, then top with the remaining batter.
Bake for 30 - 35 minutes. The centre will still be jiggly, but will firm up as the caramel layer cools. Allow to cool completely in the fridge or freezer before cutting into bars.
Video
Notes
Brownies stay fresh stored in an airtight container in the fridge for up to 1 week. They also freeze well for up to 3 months. Thaw overnight in the fridge before serving.