Preheat the oven to 325°F (160°C). Lightly grease an 8x4-inch mini loaf pan to prevent sticking.
Combine the butter, brown sugar, molasses, corn syrup, and milk in a small saucepan. Heat the mixture until it comes to a gentle boil, then remove from the stove and let it cool slightly.
In a large mixing bowl, sift together the flour, baking soda, ground ginger, and ground allspice.
Gradually add the warm liquid mixture to the bowl of dry ingredients. Stir until just combined, making sure not to overmix. Pour the batter into the prepared loaf pan.
Bake the loaf for about 1 hour until the top is firm and bounces back when lightly pressed.
While the loaf cools, beat the softened cream cheese in a bowl until smooth. Gradually add the powdered sugar and vanilla extract, mixing until creamy. If the frosting is too thick, add 1-2 tablespoons of milk to reach the desired consistency.
Once the loaf has completely cooled, spread the cream cheese frosting evenly. Slice and enjoy.
Notes
Sift the dry ingredients. This will help avoid any lumps in the batter.When combining the butter, brown sugar, molasses, corn syrup and milk, bring to a boil then remove and let cool off.Do not overmix the batter. Overmixing can lend to a touch loaf so only mix until combined.Check for doneness. The top of the loaf should be firm with a little bit of give when you press on it. Place a toothpick in the center to see if it comes out clean.For the cream cheese icing, use softened cream cheese for best results.