Preheat oven to 400°F (200°C).
Spread pecans on a baking sheet and toast for 5–7 minutes. Cool completely and roughly chop.
Line a baking sheet with parchment paper.
Whisk flour, brown sugar, baking powder, cinnamon, and salt together in a large bowl.
Add cold cubed butter and cut it into the flour until the mixture contains crumbs and pea-sized pieces of butter.
Stir in ¾ cup cooled toasted pecans.
In another bowl, whisk cold heavy cream, egg, maple syrup, and vanilla.
Pour the wet ingredients over the flour mixture.
Stir gently just until a shaggy dough begins to form.
Turn onto a lightly floured work surface and gently bring the dough together without kneading excessively.
Shape into an approximately 7-inch-wide, 1-inch-thick disc.
Cut into 8 wedges.
Transfer the wedges to the prepared baking sheet, leaving space between them.
Refrigerate for 15 minutes.
Lightly brush the tops with heavy cream.
Bake for approximately 18–22 minutes, until risen and golden around the edges.
Transfer to a wire rack and cool for 10–15 minutes.
Whisk powdered sugar, maple syrup, 1 tablespoon heavy cream, vanilla, and salt until smooth. Add additional cream only as needed.
Drizzle glaze over the slightly cooled scones.
Sprinkle with additional toasted pecans and allow the glaze to set slightly before serving.