When I saw a picture of extremely tall, extremely flaky "blitz biscuits" in my new copy of Crust & Crumb, I immediately thought of making turnovers with them instead. Having now made the dough into both biscuits and turnovers, I can report that it is a splendid turnover dough, but actually too flaky for optimal biscuits. If you want to try the biscuits though, the procedure is all the same, but cut your preferred size and shape of biscuit out of 1/2"-tall dough instead.
Also, the bread book is excellent, as anticipated. I've been working on the baguette recipe and I'll post it when I've gotten the crumb to be a bit less gummy, which will hopefully be soon!
2 + 1/3 c flour (12 oz)
1.5 t baking powder
1/4 t baking soda
1/4 t salt
2 sticks cold salted butter (or increase the salt if using unsalted)
1 c cold buttermilk
2 tart baking apples (1 lb total)
3/4 c sugar
1.5 t lemon juice
1/4 t salt
cinnamon sugar for topping
Combine the dry ingredients (flour through salt) in a bowl. Cut each stick of butter in half length-wise, then slice into thin-ish slices. Toss the butter into the flour and rub the butter and flour together with your fingertips to break down the butter into small but not too small pieces (the book says "dime-size"). Stir in the buttermilk until a dough forms. Turn out onto a floured surface and roll into a 1/2"-tall rectangle. Fold in thirds like a letter, roll out again, and fold in thirds the other direction. Wrap the dough in plastic wrap and put in the fridge for at least 20 minutes.
While the dough is chilling, make the filling. Peel the apples and grate them in the food processor, then combine the apple with the rest of the ingredients (sugar, lemon, salt). Place in a colander and squeeze out all the excess juice. (I didn't save the juice but I'm sure there's something good you could do with it.) Set aside or refrigerate until ready to use.
Take the dough out of the fridge and place it back on the floured surface. Roll out to 1/2" and fold in thirds as before. Roll out into a rectangle again, but thin this time, about as thin as pie dough (maybe 1/8" high?). Cut into ~18 ~4"x4" squares with a sharp knife. Place a spoonful of dry apple filling in the center of each square; don't overfill the turnovers even if you have extra filling. With each pastry, fold one corner over to the opposite corner to make a triangle, and press the seams together with your fingertips. Transfer to a parchment-lined baking sheet and chill in the fridge for at least 20 minutes.
Position one rack in the middle of the oven, and preheat the oven to 500F. When the oven is very hot, quickly put one pan of turnovers on the rack and turn the heat down to 450F. You want it to be very hot both above and below the pan so the butter goes into making flaky pastry layers instead of melting out into a little sizzling pool around each turnover, but some meltiness is probably unavoidable. Bake for 15 minutes or until golden brown on all sides. (If you have two pans, let the oven get back up to temperature before putting the second one in.) Transfer the turnovers to cooling racks and eat while warm.