Making the pudding
Put the cornstarch and water in a small jar with a tight lid, seal the jar and shake the mixture until well combined.
Pour the eggnog into a medium saucepan and bring to a light simmer, adding the cornstarch mixture a little at a time, constantly whisking until mixture starts to thicken. Remove from heat and allow to cool. Pudding will become slightly thicker as it cools. Refrigerate until ready to make the parfaits.Assembling the parfait
Place a layer of raspberries or sliced strawberries in the bottom of each glass. Add a layer of the pudding, a tablespoon of cookies and more fruit; repeat to fill glass. Top with a dollop of whipped cream and drizzle the caramel sauce over the whipped cream.