Chocolate-Dipped Salted Caramel Marshmallows

INGREDIENTS

• 1 1/2 cups granulated sugar
• About 6 ounces bittersweet chocolate, finely chopped
• 1 tablespoon pure vanilla extract
• Flaky sea salt, such as Maldon, for garnish
• About 1 cup confectioners' sugar for coating pan and marshmallows
• 1 cup light corn syrup
• 1 teaspoon fine sea salt
• 4 (1/4-ounce) envelopes powdered unflavored gelatin
• 1 1/2 tablespoons vegetable shortening, preferably trans-fat-free
• Vegetable oil for brushing pan