Preparation Steps

• Line an 8x8 inch baking pan with parchment paper, leaving an overhang on all sides. Lightly grease the parchment paper.
• In a small saucepan, combine granulated sugar, corn syrup, and water. Heat over medium heat, stirring until sugar dissolves. Cook without stirring until the mixture reaches 240°F (115°C) on a candy thermometer.
• While the syrup is cooking, whip the egg whites with cream of tartar in a clean, dry bowl of a stand mixer until soft peaks form.
• Once the syrup reaches 240°F, slowly and carefully pour it in a thin stream into the whipping egg whites while the mixer is running on medium-high speed. Continue to whip until the mixture is thick, glossy, and has cooled to room temperature (about 10-15 minutes).
• Fold in the strawberry puree and vanilla extract until just combined.
• Pour the marshmallow mixture into the prepared pan and spread evenly. Let it set at room temperature for at least 4 hours, or preferably overnight.
• Combine powdered sugar and cornstarch in a small bowl. Dust your work surface and a sharp knife or pizza cutter with the mixture.
• Lift the marshmallow slab out of the pan using the parchment paper overhang. Cut into desired shapes. Dust all sides of the marshmallows with the powdered sugar-cornstarch mixture to prevent sticking.