Mrs Durkin's Fudge cake

The combination of sour milk and baking soda creates a chemical reaction that produces carbon dioxide, leavening the cake while tenderizing the crumb through acidification. Adding hot water at the end creates a thin batter that gelatinizes the starches and dissolves the cocoa completely, resulting in a moist, fudgy texture. The low oven temperature prevents the exterior from setting too quickly, allowing the cake to rise evenly and develop its characteristic dense, brownie-like consistency.