1.5 oz (one jigger) Laird's blended applejack
1.5 oz (one jigger) Campari
.75 oz (half jigger) Punt y Mes
.75 oz (half jigger) Luxardo Maraschino
.75 oz (half jigger) Grand Marnier
Pour into cocktail shaker with ice, shake, strain, drink. If desired, swap jiggers for ounces for something less sledgehammery. It's a lot of alcohol, otherwise. The original recipe used Aperol in place of Campari, which is much less alcoholic. (Though it also used 100 proof rye rather than 80 proof applejack.)
This would probably be faaaaabulous with bonded (i.e. all-applejack) applejack, but I don't have any. Might need to drop the amount of one or more of the sweet things (grand marnier & maraschino) in that case, because the applejack will be supplying enough fruit to beat the Campari into submission. It's sweet as-is by my standards, but my standards classify Manhattans are sweet drinks.
Note on the drink name -- the ES drink is named the Prospect Park in the grand tradition of naming Manhattan variants for other NYC locations. This one, however, is named for the park in Somerville, 'cause I used to live up on Prospect Hill.
The origin story: after my b'day party at Eastern Standard, I eventually managed to buy all the ingredients for the Prospect Park (except the Rittenhouse 100 proof -- I use Old Overholt as my mixing rye in everything and it's lovely there). And then, since Aperol is like Campari's idiot kid brother, after I ran out of rye one day I started wondering if applejack's fruit would stand up to Campari or not. So I mixed it up as the Prospect Park (which is 3 parts aperol 3 parts rye 1 part punt y mes 1 part maraschino) but went heavy on the sweet things and the answer was still "not without more help". So I dropped in the Grand Marnier. And then it worked.