Toast the sliced almonds in a dry skillet over medium heat for 3-4 minutes, stirring frequently, until golden and fragrant. Transfer to a plate to cool completely.
In a large chilled bowl, beat the heavy cream with an electric mixer on medium speed until it begins to thicken, about 1 minute. Add the powdered sugar, vanilla extract, and almond extract.
Continue beating on medium-high speed until soft peaks form, about 2-3 minutes. Do not overbeat or the cream will become grainy. The peaks should curl when you lift the beater.
Drain the cherries thoroughly in a colander, then pat dry with paper towels to remove excess moisture.
Assemble the parfaits in 6 clear glass cups or mason jars. Start with 2 tablespoons whipped cream in the bottom of each cup.
Add a layer of cherries (about 5-6 halves per cup), followed by a sprinkle of toasted almonds and optional crushed wafer cookies.
Repeat with another layer of whipped cream, cherries, and almonds. Finish with a generous dollop of whipped cream on top.
Garnish each parfait with a final sprinkle of toasted almonds and one whole cherry. Cover loosely with plastic wrap.
Refrigerate for at least 30 minutes to let the flavors meld, or up to 6 hours before serving. Serve chilled with long spoons.
