Heat oven to 400 degrees F.
In mixing bowl, whisk together all dry ingredients (minus the powdered sugar - that's for the drizzle.
In small mixing bowl, stir together pumpkin puree, half and half, vanilla. Set aside.
Grate 3 tablespoons of the butter and cube 4 tablespoons of the remaining butter. Add butter to the dry mixture. With fingers, working quickly, work butter into the mixture by pressing butter with flour between thumbs and fingertips for about 2-3 minutes, until only small pea-sized pieces of butter remain visible.
Make a well in the center of the flour mixture and pour pumpkin mixture inside. Stir gently with spatula until combined (about 30 seconds). If there is still loose flour, add a little more half and half and then knead gently (with hands) inside the bowl until mixture holds together.
Turn mixture out onto lightly floured surface and form dough into 8-inch disk. It should be about an inch and a half thick.
With floured knife, slice into 8 pieces (like a pie). Transfer pieces to parchment paper-lined baking sheet.
In small bowl, whisk together egg and 1 Tbsp of heavy cream for egg wash. Brush tops of each scone.
Bake for about 15 minutes until corners are light golden brown. Let cool.