Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.

In a large mixing bowl, whisk together flour, granulated sugar, baking powder, cinnamon, nutmeg, and sea salt.

Grate the frozen stick of butter using large holes of a box grater directly into dry ingredients. Toss lightly with fingers until butter is coated and resembles coarse pea-sized crumbs. Fold in diced apples.

In a separate measuring cup, whisk together cold heavy cream, egg, and vanilla extract. Pour over dry ingredients.

Gently fold with a fork just until a shaggy dough begins to form. Turn out onto a lightly floured surface and gently bring together into an 8-inch round disc (about ¾-inch thick). Do not knead or overwork!

Using a sharp floured knife or bench scraper, slice disc cleanly into 8 triangular wedges. Arrange wedges 2 inches apart on prepared baking sheet.

Brush tops lightly with 1 tablespoon heavy cream and sprinkle with coarse sparkling sugar if desired. Chill baking sheet in freezer for 10 minutes to ensure maximum flakiness.

Bake at 400°F (200°C) for 18 to 22 minutes until tops are golden brown and edges are crisp. Cool on baking sheet for 5 minutes, then transfer to a wire rack.

Whisk together powdered sugar, maple syrup, heavy cream, and cinnamon until smooth. Drizzle liberally over warm scones before serving.