Make the caramel: Combine nut butter, syrup, melted coconut oil, and a pinch of salt until smooth. Adjust coconut oil as needed for desired consistency. Pour into a 6-inch square baking tray lined with greased baking paper. Freeze until set.
Preheat oven to 350°F (180°C). Line and lightly grease a 6-inch square baking tray.
Prepare the cookie dough: Cream together melted butter and sugars. Mix in yogurt, then gently fold in flour and baking soda until just combined. Stir in chocolate chips. Press dough into the base of the prepared tray and chill in the fridge.
Make the brownie batter: Melt butter and sugars in a saucepan over low heat. Stir in milk, then remove from heat and add chocolate, mixing until smooth. Sift flour, cocoa powder, and remaining sugar into a bowl. Pour in wet mixture, stirring until combined.
Assemble and bake: Remove cookie dough and frozen caramel from the fridge and freezer, respectively. Place caramel slab on cookie dough, then cover with brownie batter. Bake for 20-25 minutes until top is set and a toothpick inserted into the center comes out with moist crumbs. Let cool completely before slicing.
Serve: Enjoy these decadent treats with a scoop of ice cream for extra indulgence!