In a large bowl, combine the sourdough starter, heavy cream, egg, egg yolk, canned pumpkin, and vanilla extract.
In a separate bowl, combine the flour, sugar, salt, baking powder, baking soda, cinnamon, ground cloves, and nutmeg.
Grate the frozen butter and add it to the bowl with the dry ingredients in 2-3 increments.
Add the wet ingredients to the dry ingredients and combine until the dry ingredients are just incorporated.
Turn the dough out onto a floured surface, shape into a disc that is 9 inches in diameter and roughly 1 inch high. Use a bench scraper to divide the dough into 8 slices. Place them on a baking sheet and freeze for 20 minutes.
Preheat the oven to 400°F. Remove the scones from the freezer, brush with heavy cream, and bake for 16-18 minutes.
While the scones are cooling, make the maple icing. Combine the maple syrup and powdered sugar in a medium bowl. Drizzle on the scones.
Notes
Extra Egg Yolk: Most scone recipes use just one egg, but I like to toss in an extra yolk. It gives the scones a deeper flavor and a richer texture that I really enjoy.
Heavy Cream vs. Buttermilk: I've tried baking scones with both heavy cream and buttermilk, and the heavy cream always wins in my book. It has a higher fat content, which makes the scones taste more luxurious and gives them a crisper exterior. Buttermilk still works, but the results are a little softer and less rich.
Cold Ingredients: Using cold ingredients—especially frozen butter—is key. Putting them in the freezer for a short while before baking helps the scones keep their shape and rise nicely.
Avoid Overmixing: When mixing your dough, less is more. Overworking it leads to dense, tough scones.
Easy on the Extra Flour: It’s tempting to sprinkle on a lot of flour while shaping the dough, but resist the urge. Too much extra flour dries the scones out.
Watch the Bake Time: Scones can go from perfect to dry in under a minute. Keep a close eye on them, and remember that every oven is a little different. Yours might need a minute more or less than the recipe says.
Brushing the Tops: You’ve got options here—heavy cream, leftover egg white, or nothing at all. I’ve tested them all. My favorite is brushing with heavy cream; it gives the tops a soft sheen with a slightly rustic finish. Egg white makes them shinier and more polished-looking. Skipping it all altogether still works fine. They’ll taste just as good, but won’t have that same golden glow.