Preheat oven to 200°F.
Add egg whites to a clean mixing bowl.
Use an electric mixer and beat egg whites on medium speed until foamy.
Add cream of tartar and continue beating until they hold soft peaks.
Slowly add the granulated sugar, beat until meringues hold stiff peaks. Beat in vanilla.
Line a baking sheet with parchment or silicone baking mat. Spoon or pipe meringues into 12 equal mounds. Bake for approximately 1 ½ to 1 ¾ hours. The meringues are done when the outsides are dry and crisp and separate easily from the parchment paper. Meringues can be stored in an airtight container for several days.
Mix strawberry slices and Unicoi Preserves together in a medium mixing bowl, set aside.
In a large bowl, whip heavy whipping cream and powdered sugar with a hand mixer until stiff peaks form.
To serve: Crumble 6 meringues into whipped cream, then fold in most of the sliced strawberries, reserving some for garnish. Spoon into dessert cups, garnishing with reserved strawberry slices and additional crumbled meringue. Serve immediately.
Notes: This is a great do ahead dessert! You can make all three components of Suzy’s Eton Mess ahead, then just assemble it when you’re ready to serve.