Walnut Cheddar Scones - Diamond Nuts

Ingredients

• 3 cups all-purpose flour, plus more for dusting
• 1 tablespoon baking powder
• 1/2 teaspoon baking soda
• 1 tablespoon sugar
• 1 1/2 teaspoons salt
• 8 tablespoons cold butter, cut into cubes
• 2 cups grated cheddar cheese
• 1 cup Diamond of California chopped walnuts, toasted
• 4 green onion tops sliced
• 1 - 11/4 cups cold half & half, divided
• 1 egg yolk