Sift cocoa powder and sugars in to a large bowl
Add in remaining ingredients and using a hand mixer, mix until ingredients are well combined and the sugars have completely dissolved
Cover with plastic wrap and refrigerate (if using an ice cream maker) for an hour OR if using no-churn method, place mixture in freezer, covered until ice cream is roughly 80% frozen - start checking on ice cream after ~4 hours
If using an ice cream maker, add liquid to bowl and churn until your mixture is thick
Once ice cream is ready either via freezer or churning, cut up brownies into 1" chunks and stir into ice cream. Add 4 tablespoons of caramel and 1/2 cup of walnuts, swirl to gently combine. Return to freezer for at least 2 hours or until ice cream as fully solidified.