Preheat oven to 350 degrees. Spray mini loaf pans with flour-added cooking spray or grease and flour. I used 4 loaf pans that were about 3 ½ by 5. You can make these smaller (see cook times at bottom)
Cream the butter and brown sugar until light. Beat in eggs, 1 at a time; beat in molasses. Stir together flour, ginger, baking soda and baking powder, cinnamon, nutmeg, allspice, salt and pepper; stir one-third into butter mixture. Stir in pumpkin. Stir in another third of the flour mixture; stir in buttermilk, then remaining flour mixture.
Scrape batter into prepared pans and bake on center rack. If using 2 ½ x 3 ½ loaves, check at 30 minutes. For slightly larger loaves, check at 37 minutes. For one giant 9x6 inch loaf, test at 40 minutes
A toothpick or chopstick (I use a chopstick) inserted should come out clean. Let cool. Turn from pans and let cool completely. Ice when cool.
To make the icing, melt the butter in a microwave-safe bowl. Add the sugar and stir to coat it with butter – it will be thick and pasty. Slowly add the lemon juice one tablespoon at a time, mixing well and adding more juice until you get the consistency you like. I mix it so that it flows off a spoon, then I let it stand for a bit so that it’s thickens up slightly. When the pumpkin loaves are completely cool, drizzle the icing on top or put it in a heavy duty zipper bag, snip off the corner, and drizzle it over in a lattice shape.