Brownie Preparation

1. Preheat your oven to 350°F (175°C). Grease an 8×8 or 9×9 pan and line it with parchment paper.
2. Melt the butter in a mixing bowl. Whisk in brown sugar and granulated sugar while still warm.
3. Add in the eggs and vanilla, whisk until glossy and thicker.
4. Sift and mix in cocoa powder, flour, salt, and spices.
5. Stir in molasses until no dry streaks remain; avoid overmixing.
6. Pour brownie batter into the prepared pan and smooth the top.

Baking

1. Bake the brownies in the oven for 22-30 minutes, checking for doneness with a toothpick. It should have a few moist crumbs.
2. Let the brownies cool in the pan before frosting.

Frosting Preparation

1. In a small saucepan, whisk flour and milk until smooth; cook over medium heat until it thickens.
2. Transfer the mixture to a bowl and cover with plastic wrap to cool completely.
3. In a mixing bowl, cream together softened butter and sugar until fluffy.
4. Add the cooled flour mixture to the creamed butter, one spoonful at a time, until silky.
5. Mix in vanilla, salt, and spices. Adjust flavors to taste.

Final Assembly

1. Spread the frosting over the cooled brownies.
2. Chill the frosted brownies for 20-30 minutes to make cutting easier.
3. Cut into squares using a sharp knife, wiping the blade between cuts for clean edges.