Preheat your oven to 250°F and line a rimmed baking sheet with parchment paper.
Whisk cornstarch and 1 3/4 cups sugar in a small bowl.
Beat egg whites, lemon juice and salt in an electric mixer on medium (about 1-2 minutes, until frothy). Increase speed to medium-high and slowly add the cornstarch/sugar mixture. Beat for about 10 minutes until stiff peaks are formed.
Form the meringue into a 13x10-inch rectangle on the parchment paper. Bake at 250°F until firm (approximately 2 hours and 30 minutes). Next, turn off the oven and let stand in oven until it's completely cool (another 3 hours).
Combine strawberries, basil and vinegar and let sit for 30 minutes.
When you're ready to serve it, beat the heavy cream with 1 Tbsp sugar in the mixer on medium-high speed until soft peaks form. Spread evenly over the meringue. Top with strawberry balsamic mixture and serve immediately.