For best results, chill the bowl and whisk you are going to use to whip your heavy cream in your refrigerator or freezer, and let ice cream sit out about 10-15 minutes on your counter prior. I use a stand mixer but you can also whisk by hand or use a hand mixer. For extra deliciousness, scout out your local area for a dairy or creamery where you can buy homemade ice cream.
Prepare toppings: Spread pecans in an even layer on small baking sheet and toast nuts until golden and fragrant, about 3-5 minutes, in a toaster oven or conventional oven set to 350 °F. Monitor the nuts to make sure they do not burn; stir after 3 minutes and check for doneness. Set aside to cool. Once nuts are cooled, coarsely chop.
As nuts are cooking, drain about 3 tablespoons of cherries from the jar, reserving liquid. Coarsely chop cherries and chop chocolate; set both aside. If using, stir kirsch into reserved cherry juice.
Make homemade whipped cream: Beat heavy cream with powdered sugar and vanilla in chilled bowl of stand mixer using chilled whisk attachment (see note at beginning of recipe.) Add more sugar if you like your whipped cream sweeter. Once the cream is beaten to a firm consistency that will hold its shape (but don't go too far, otherwise you'll start to make butter!), fold in about 1 tablespoon of syrup from jar of cherries.
Assemble parfait: Add 1 scoop of ice cream to a glass, followed by about a tablespoon each of cherries, chopped chocolate, and nuts. Top with whipped cream and a drizzle of cherry syrup. Repeat once more and serve immediately.