Toast pecans at 350°F for about 5 minutes. Set aside to cool.
Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
Whisk together flour, baking powder, salt, and all of the spices.
Add the cold butter to the dry ingredients and toss to coat. Using your fingers or a pastry cutter, break the butter down into the dry ingredients. Work very quickly so that the butter remains cold. Some of the butter will be the size of oat flakes, others will be the size of peas. Set aside in the fridge to stay chilled.
In another bowl, whisk together the half-and-half, pumpkin puree, maple syrup, and vanilla extract.
Add the pecans to the dry ingredients and stir with a fork.
Add the wet ingredients, all at once, to the dry ingredients. Stir together with a fork until almost thoroughly combined. Using a large ice cream scoop, scoop scones dough by the 1/2-cupful onto the prepared baking sheet. Leave about 2 inches of space between each scone.
Bake for 18 to 20 minutes or until browned slightly with dry tops. Allow to cool completely before glazing.
To make the glaze, beat all the ingredients together with a spoon. Thin with more maple syrup if it’s too thick to drizzle. Evenly drizzle scones with glaze.