Preheat oven to 400°F.
Combine pastry flour, salt, and baking powder in a medium sized bowl.
Add chilled honey butter and toss it with the flour mixture, pinching and smushing it between your fingers until the butter pieces are the size of large peas or small grapes.
Fold in the cold buttermilk, stirring gently just until the buttermilk is absorbed. The mixture will be clumpy and have lots of dry floury bits, but that's okay. Do not overmix!
Turn the mixture out onto a lightly floured counter or cutting board. Gather it into a pile in the center and use a bench scraper to cut a cross hatch pattern through it. Then use your hand and the straight edge of the bench scraper to form a long rectangle about ½" high.It doesn't have to look pretty. Work quickly so the butter doesn't start to melt.
Fold the top third of the dough rectangle down. Then fold the bottom third of dough up over it in a letter fold. It will be messy. That's okay.
Slide the bench scraper under the folded dough packet and rotate it 90 degrees. Pat it out into a long rectangle about ½" high and repeat the folding process.
Rotate 90 degrees again. The dough will be much smoother and more cohesive now. If it's still crumbly, repeat the folding process one more time.
Pat the dough out into a long rectangle about 6 inches across and 1 inch high. Trim the edges to release the tension from where the dough was folded. Pat the excess dough on top of the dough rectangle.
Cut the dough rectangle into 18 mini biscuits — a 3 by 6 grid. Cut in an up and down motion, not slicing or sliding the blade on the counter.
Transfer biscuits to a lined baking sheet about 2" apart. Brush just the tops with egg wash and sprinkle with flaky salt.If the butter seems warm or you're waiting for the oven to finish preheating, pop the sheet pan in the fridge or freezer until you're ready to bake.
Bake TK minutes at 400°F. After 10 minutes, spoon melted honey butter over the biscuits and return to the oven for an additional 2-3 minutes.