Preheat oven to 400 degrees F. Line a baking sheet with parchment paper. Sift together flour, sugar, baking powder, salt and baking soda into a large bowl. Add butter and mix in with a pastry cutter until mixture resembles coarse meal. Mix in white chocolate chips and crushed candy canes. Gradually add buttermilk and peppermint extract, tossing with a fork until moist clumps form. Turn dough out onto lightly floured surface. Knead briefly to bind dough, maybe 4 turns. Form dough into 1 inch thick rectangle. Cut rectangle in half lengthwise, then cut out squares. Then, cut squares at a diagonal making a triangle. Transfer wedges to prepared baking sheet, spacing 2 inches apart. Bake until tops of scones are golden brown, about 25 minutes.