Combine walnuts with 1/2 cup sugar in a medium sauce pot over medium-high heat.
Stir constantly until the sugar dissolves and coats the nuts in caramel. Pour nuts onto a nonstick silicon mat or a sheet of parchment paper.
Combine flour, 3 tbsp sugar, kosher salt, cinnamon, most of the candied walnuts, and baking powder in a large bowl. Chop butter into small squares and chill for 5 minutes in the freezer.
Combine heavy cream, vanilla, sour cream, egg, and 1 tbsp maple syrup in a separate bowl or pyrex. Mix until combined.
Remove butter from freezer and add to the flour mixture. Quickly massage butter into flour until you have a sandy, crumby mixture.
Add your liquid ingredients and stir just to combine into a shaggy dough. Dump dough onto a clean work surface and bring together into a 16" disc (making sure no bits of flour remain.
Cut your disc into 6 equal triangles and place on a parchment-lined baking sheet. Chill scones in fridge for at least 15-20 minutes before baking.
Preheat oven to 400°F. Brush each scone in about a teaspoon of heavy cream with a pastry brush. Sprinkle Turbinado sugar evenly over the tops and bake for 30-35 minutes until golden brown.
Let scones cool. Combine 3/4 cup powdered sugar, 1/3 cup maple syrup, and a pinch of salt in a medium bowl. Whisk until combined into a smooth glaze.
Dip each cooled scone into the glaze and let cool. Garnish with a candied walnut and serve warm.