Mix all the dry ingredients in a medium bowl until well combined. Using a pastry knife or a food processor, cut butter into dry ingredients until the butter is the size of small peas (using a processor will produce more fine pieces).
Mix walnuts into flour and butter until combined.
Reserve 2 tablespoons of the cream in a cup or small bowl. In another bowl, whisk the remaining heavy cream, egg, and butterscotch flavoring to combine.
Add the wet ingredients to the dry ingredients in the larger bowl and stir to combine. The dough will begin to hold together and may be somewhat stiff, depending on the flour mix used. If the dough is too dry, add a small amount of cream and mix-in.
Divide dough into two equal parts. Sprinkle a small amount of GF flour mix to lightly dust the counter and place half the dough on the flour. Press dough into a disc approximately 6 inches wide and 1 inch thick. With a sharp knife, cut the circle into 8 equal pieces.
Place the dough pieces on a parchment lined baking sheet 2 inches apart. Brush tops with reserved cream and bake for 10-12 minutes and light-golden browned.
Serve with whipped cream or butter and jam.
Notes
Omit xanthan gum if it is included in the gluten-free flour mix.
All-purpose gluten-free flours mixes each produce different results in baked goods, depending on flour mix. I have had consistent results with King Arthur gluten-free flour mix.