Thoroughly mix the flour, sugar, baking powder, baking soda and salt in a large mixing bowl.
Add the shortening and butter to the dry mixture, and with a pastry cutter or your fingers, work the fat into the flour mixture until crumbly. Add the yeast and stir well.
Add the vanilla to 3/4 cup of the buttermilk, then pour and stir to make soft dough. Add the other 2 tablespoons of milk only if the dough seems very dry.
Add ½ cup of the frozen berries and carefully stir them into the dough.
Turn mixture onto a floured surface and shape into two 6x3 inch rectangles.
With a floured knife, cut each rectangle into 8 small triangles.
Arrange scone triangles on a nonstick or parchment lined baking sheet and poke the remaining blueberries into the scones. Cover loosely with parchment or nonstick foil and let sit for 1 hour to rise. After one hour, put the risen triangles (they won’t rise dramatically, but they will lighten) in the freezer for another hour or until you are ready to bake them.
Preheat oven to 400 degrees F.
Arrange as many triangles as you want to serve on a parchment lined baking sheet and bake for 18-20 minutes or until golden and inside appears cooked through.
Brush tops with melted butter and serve warm or let cool and drizzle with icing.
McCormick’s Imitation Butternut & Vanilla extract, which is hard to find in Austin and which I have to order via Amazon, tastes great in these scones, but if you don’t have any, regular vanilla is fine.