Seared Bologna, Egg, and Cheese Biscuit Sandwiches with Sweet Mustard

Ingredients

• 7 ¹⁄₂ cups (2 lb. 4 oz.) all-purpose flour, plus more for dusting and rolling
• ¹⁄₂ cup plus 1 Tbsp. (4½ oz.) sugar
• 2 tbsp. kosher salt
• ¹⁄₄ cup plus 2 tsp. baking powder
• 4 ¹⁄₂ sticks (1 lb. 2 oz.) cold unsalted butter, cut into small cubes
• 3 large eggs
• 2 cups sour cream
• ³⁄₄ cup whole milk
• For the sweet mustard:
• ¹⁄₂ cup distilled white vinegar
• ¹⁄₂ cup sugar
• ¹⁄₂ cup mustard powder, such as Colman’s brand
• 1 ¹⁄₂ tsp. kosher salt
• For the sandwiches:
• 1 tbsp. vegetable oil, divided
• Twelve ¼-inch-thick slices bologna
• 12 large eggs
• Kosher salt
• Freshly ground black pepper
• 12 slices American cheese