Combine both sugars and 1 cup water in a small saucepot. Bring to a boil, stirring occasionally, and boil for 3 minutes or until you achieve a syrup-like consistency
To serve, fill a tall glass with ice. Add the Cold Brew. Sweeten with the homemade syrup to taste
Pour in just enough creamer to create a marbling effect in the glass. Be sure to fill the glass completely, then spoon a large dollop of marshmallow crème onto the top of the glass and spread edge-to-edge
Use a kitchen torch to toast the marshmallow topping