Preheat the oven to 180C/350F/Gas 4. Line an 8x8-inch square baking pan with foil or parchment paper. Set aside.

Whisk together the flour, baking powder, baking soda, and salt. Set aside.

Whisk together the butter and sugars until combined. Add the egg, and vanilla, and mix until combined. Add the dry ingredients, and mix until just combined. Fold in the chocolate chips.

Press the dough into the prepared pan. If the dough is too sticky to work with, use floured hands to press it in.

Place the caramels and milk in a microwave-safe bowl, and heat in 30 second intervals, stirring after each one, until melted and smooth.

Spread the caramel evenly over the cookie dough layer. Refrigerate whilst preparing the brownie batter.

Place the butter, sugar, cocoa powder, and salt into a microwave-safe bowl. Heat for 30 seconds, then stir to combine. Heat for another 30 seconds to 1 minute until the mixture is very warm/hot to the touch.

Mix in the egg 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 the batter over the caramel layer, and gently spread out evenly.

Bake for 40 - 45 minutes or until the centre is set, and no longer jiggly. Allow to cool completely in the pan on a wire rack before cutting into bars.