Make the Butterscotch Sauce: Add all the ingredients to a saucepan and cook on medium-high heat while stirring until the butter melts. Once the sauce starts boiling, bring the heat down and let it simmer for 2-3 minutes until the sauce thickens. Take off the heat and let it cool and thicken before using.
For an oozy filling, spread a thick layer of the butterscotch sauce on baking paper slightly smaller in size than your baking pan and freeze it until completely set.
Preheat your oven to 180 degrees Celsius. Line your brownie pan with baking paper/wax paper to avoid the brownie from sticking to the pan. Leave an overhang of baking paper on either side – this makes it easy to lift the brownies from the pan.
Melt your chocolate with butter in a microwave-safe bowl or over a double boiler* until the ingredients are fully melted and combined.
Add granulated sugar to the chocolate mix and stir it with a whisk until combined while it’s still hot.* (PS: the sugar will not dissolve completely, so don’t worry if the batter looks grainy at this point)
Once the sugar is combined, add the eggs and vanilla extract and whisk it again until they are well incorporated into the chocolate batter.
Add the dry ingredients - flour, cocoa powder, salt, coffee powder, and chocolate chips, and fold it gently with a spatula into the batter until completely combined.
Assemble the brownie: transfer half the batter to the baking pan, spread an even layer, then top it with the butterscotch sauce. If using the frozen butterscotch method, place the layer on top of the brownie batter and cover it with the remaining batter evenly. If using the chunk method, add dollops of soft butterscotch sauce on the bottom brownie batter layer, spread it, and top it with the remaining brownie batter.
Bake it for about 4-50 minutes, until the brownies are cooked but still fudgy.* Once your top looks set and the test toothpick has some crumbs, your brownie is ready. Let the brownies cool completely before slicing.