Cheddar Shortcakes with Corned Beef Hash

INGREDIENTS

• 2 red bell peppers, coarsely chopped
• 1/2 cup minced fresh flat-leaf parsley
• 3 tablespoons cold unsalted butter, cut into bits
• 1 lb (1/8-inch-thick) slices cooked corned beef, cut crosswise into 1/8-inch-wide strips
• 3/4 stick (6 tablespoons) unsalted butter
• 2 onions, coarsely chopped
• 3 cups all-purpose flour
• 3/4 cup water
• 2 lb yellow-fleshed potatoes such as Yukon Gold
• 1 1/2 teaspoons salt
• 1 teaspoon baking soda
• Accompaniment:
• 1 cup sour cream
• 1/2 teaspoon black pepper
• 1 teaspoon salt
• 6 oz sharp Cheddar, coarsely grated (1 1/2 cups)
• 1 1/2 teaspoons baking powder