In a medium, heavy-bottomed saucepan, combine 8 ounces roughly chopped strawberries, 1/2 cup granulated sugar, 1/2 cup heavy cream, 1 tablespoon cornstarch, 1/2 teaspoon pure vanilla extract, and a pinch of kosher salt. Cook over medium heat, whisking constantly to prevent the fruit from burning, about 8 to 10 minutes. At this point, the strawberries should break down, and the mixture should thicken to a point where the whisk leaves a trail. If it's still too thin or still too lumpy from the strawberries, continue cooking until thick and smooth. Remove from heat and cool to room temperature before using for the popsicles.