Gluten-Free Hamburger Buns Gelson's

Ingredients

• 2 tsp granulated sugar
• 1 ½ tsp active dry yeast
• 1 ½ cups warm water (about 110º), divided, plus more for molding
• 2 cups Cup4Cup gluten-free flour
• 1 cup cornstarch
• 1 Tbsp kosher salt
• ¼ tsp xanthan gum
• 7 Tbsp unsalted butter, melted and cooled slightly, plus more as needed
• 2 Tbsp honey
• 1 large Gelson’s egg plus 2 egg whites