• Nonstick vegetable oil spray
• 1.5 cups water
• 1 T Earl Grey
• 3 1/4-ounce envelopes unflavored gelatin
• 2 cups sugar
• 2/3 cup light corn syrup
• 1/4 teaspoon salt
• 2 teaspoons vanilla extract (optional)
• 1/2 cup corn starch
• 1/2 cup powdered sugar
• candy thermometer
• electric mixer
Line a 13x9x2 inch pan with parchment paper or foil. Coat lightly with nonstick spray. Bring the 1.5 cups of water to a boil and add the Earl Grey (variations: try 2 T dried lavender or hibiscus or 1 T of a different tea). Remove from heat and steep covered 10 minutes (I steep for 30 minutes if using dried flowers).
Strain and measure a 1/2 cup of the tea into a bowl and chill in the refrigerator or freezer until very cold. Measure another 1/2 cup of tea into a heavy medium saucepan. Discard extra tea (or drink it!) Once the tea is chilled, pour it into the bowl of heavy-duty mixer fitted with whisk attachment. Sprinkle gelatin over water. Let stand until gelatin softens and absorbs water, at least 15 minutes.
Combine 2 cups sugar, corn syrup, and salt with the tea in the saucepan. Stir over medium-low heat until sugar dissolves. Attach a candy thermometer to side of pan. Increase heat and bring syrup to boil. Boil, without stirring, until syrup reaches 235-240ºF, about 8 minutes.
With mixer running at low speed, slowly pour hot syrup into gelatin mixture in thin stream down side of bowl (avoid pouring syrup onto whisk, as it may splash). Gradually increase speed to high and beat until mixture is very thick and stiff, about 15 minutes. Add in the vanilla extract if using and beat about 30 seconds longer. It will be voluminous & white, begin to pull away from the sides of the bowl, and will fall very slowly in a thick ribbon when the whisk is lifted when done.
Scrape marshmallow mixture into prepared pan with a wet spatula, work quickly as it gets harder to work with if it sits—and by harder I mean almost impossible. Smooth top with wet spatula. Let stand uncovered at room temperature until firm, about 4 hours or overnight.
Sift corn starch and powdered sugar together in a bowl. Sift generous dusting of starch-sugar mixture onto work surface, forming rectangle slightly larger than 13x9 inches. Turn marshmallow slab out onto starch-sugar mixture; peel off parchment or foil. Sift more starch-sugar mixture over marshmallow slab.
Coat large sharp knife (or cookie cutters) with water or nonstick spray. Cut marshmallows into squares or other shapes, keeping knife wet or coated. Toss each in remaining starch-sugar mixture to coat. Transfer marshmallows to rack, shaking off excess mixture. Store marshmallows in an airtight container. They will keep for about a week.
You can find details on the caramel swirl here.