PARK SLOPE Boxing Day, an oft-misunderstood holiday, doesn’t get the respect it deserves in the US. After all, what could be bad about a holiday that encourages even more post-Christmas eating and drinking? Mimic those in countries wiser than ours with Black Horse Pub’s Boxing Day celebration. The Park Slope local will be giving out free bangers and mash from 1-6pm. Show up early (10am-12pm) to make good on another English tradition – sinking a pint and watching some soccer.