Sprinkle gelatin over 1/2 cup cold water in bowl of a heavy-duty electric stand mixer. Split vanilla bean, and scrape seeds into a 4 1/2-qt. saucepan. Stir in honey, granulated sugar, and 1/2 cup water. Cover and bring to a boil over medium-high heat (about 3 minutes). Uncover and boil, stirring often, until syrup thickens and a candy thermometer registers 240° (about 8 to 12 minutes; lower heat if needed to prevent mixture from boiling over). Gradually add honey mixture to gelatin mixture, beating at low speed, using whisk attachment, 30 seconds or until blended. Increase speed to high; beat 10 to 12 minutes or until mixture cools and is thick but still pourable. (Cover with a towel to prevent splattering.) Whisk together cornstarch and powdered sugar. Dust a buttered 13- x 9-inch baking dish with 1 Tbsp. cornstarch mixture. Pour gelatin mixture into dish; smooth with lightly greased spatula. Dust with 1 1/2 Tbsp. cornstarch mixture. Cover remaining cornstarch mixture tightly; reserve. Let marshmallow mixture stand, uncovered, in a cool, dry place 8 to 14 hours or until no longer sticky. Invert onto a cutting board; cut into squares. Toss in reserved cornstarch mixture to coat. Store in an airtight container at room temperature 2 weeks.