Roast walnuts ahead of time. Place them in a dry skillet over medium-low flame. Roast, tossing occasionally, until they begin to brown and become fragrant, 4 to 6 minutes. Transfer to a plate or bowl and let them cool completely. Chop or break into small pieces.
Prep the cherries and the butter slightly ahead of time. Using a sharp knife, halve the dried cherries and place them in a small saucepan. Add the bourbon and heat over a medium flame. As it starts to bubble, reduce heat and barely simmer for 2 to 3 minutes. Transfer to a bowl and pop it in the fridge to chill for at least 10 minutes. Drain completely and keep chilled until ready to use.
Cut butter into 1/2-inch cubes, place in a bowl and pop in the freezer while you prepare the dry ingredients. (If you're not baking until later, just keep the butter in the fridge—the point is, you want the butter to stay as cold as possible until you're actually baking the scones.)
Combine flour, sugar, baking soda and salt in a food processor. Pulse several times to thoroughly mix everything. Beat egg in a bowl and add 1/3 cup half & half. Set aside.
Go time. Preheat oven to 400ºF. Line a baking sheet with parchment paper or a non-stick silicone baking mat and pop it in the fridge. Add cubed butter to dry ingredients in food processor and pulse until the mix resembles a coarse meal. This will happen deceptively quickly; I stirred the mix with a wooden spoon, expecting to find lumps of butter, but did not.
Transfer flour mix to a mixing bowl and stir in the cherries and walnuts. Pour egg/half & half mixture over everything and stir to combine. If you're still finding dry flour pockets, stir in a little more half & half, a tablespoon at a time. Your goal is a dough that barely holds together, not something that sticks to your hands. I added 2 tablespoons to get there.
With flour-dusted hands, transfer mix onto a lightly floured surface. Working quickly, form it into a ball and flatten into an 8-inch disk, slightly mounded in the center. Using a sharp knife, cut into 8 wedges.
Transfer wedges to baking sheet, leaving space between them. Brush scone tops with half & half and sprinkle with a little sugar. Bake on a center rack until golden brown, 15 to 20 minutes.
Transfer baked scones to a wire cooling rack and cool either slightly or completely, depending on your will power.