How to Make It
Preheat oven to 375°F. Line a baking sheet with parchment paper; lightly coat with cooking spray.
Stir together flour, maple sugar, baking powder, and salt in a large bowl. Add butter, and, using your fingertips, blend quickly and lightly into flour. (Don’t let it melt on your fingers.)
Add egg yolks, and stir until just combined. Stir in cranberries.
Whisk together half-and-half, sweet potato, and orange zest in a separate bowl until well combined. Gradually add wet ingredients to dry ingredients, and stir gently just until dough holds together without crumbling. Add additional milk or flour, if needed.
Transfer dough to center of prepared baking sheet, and, using oiled hands, shape dough into an 8-inch round. Slice round into 8 large wedges, pulling them apart slightly as you cut.
Lightly beat egg whites until barely foamy. Brush tops of scones with egg whites.
Bake scones in preheated oven until lightly browned, 22 to 24 minutes. Cool on baking sheet on wire rack 20 minutes before serving with Molasses-Orange Butter (recipe below). Store scones in an airtight container at room temperature up to 3 days.
Prepare the Molasses-Orange Butter: Whisk together unsalted butter, molasses, orange zest, orange juice, and sea salt in a bowl until well combined. Taste and add more salt, if desired. Store butter in refrigerator up to 1 week.