Preheat oven to 400 F (200 C). Line a baking sheet with parchment paper.
In a medium-large bowl, whisk together the flour, baking powder, and salt. Add the butter cubes, and using a pastry cutter or fork cut the butter until the pieces are no bigger than peas. Refrigerate the bowl to chill for 10 minutes.
Meanwhile, whisk together the buttermilk and honey. Add over the butter/flour mixture and stir until the dry ingredients are moistened. Knead gently about 3-4 times to bring it together.
Lightly dust with flour the working surface and roll the dough into a 9×5-inch rectangle and about 1/2-inch thick. Fold the dough into thirds like a business letter,using the long sides of the rectangle. Repeat this step, roll the dough into a 9×5-inch rectangle about 1/2-inch thick, and again fold it into thirds like a letter.
Finally roll the dough out to 3/4-inch thickness. Using a 2 inch round cutter, cut biscuits from the dough (don't twist the cutter, use a straight up and straight down motion).
Transfer to the prepared baking sheet, leaving about 1 inch of space between them. Beat the egg yolk and brush the biscuits. Sprinkle sesame and flex seeds on top of each.
Bake for about 11-12 minutes, or until the biscuits have risen and are golden brown on top.
Transfer the biscuits to a wire rack to cool for a few minutes and serve warm.