Blueberry and Rye Slab Pie

Directions

1. Crust
2. To make the crust, combine the flours and salt in a bowl. Use your fingers or a pastry cutter to cut half of the butter into the flour until it is the size of peas, then cut in the other half until it is the size lima beans. Some of the butter will be completely worked into the flour, but you should have lots of visible pieces of butter in the dough, too. Add the apple cider vinegar to the water and make a well in the center of the flour mixture. Use a gentle hand or wooden spoon to mix about 8 tablespoons of water into the flour until just combined. If the dough seems very dry, add more water a couple of teaspoons at a time. You have added enough water when you can pick up a handful of the dough and squeeze it together without it falling apart. Press the dough together, then split it in half, form into discs, and wrap each disc in plastic wrap. Chill the dough for at least one hour before using, or overnight.

1. Filling
2. Preheat oven to 400º F and line a baking sheet with parchment paper.
3. Gently toss the blueberries, sugar, flour, salt, lemon zest, ginger, and vanilla bean seeds in a bowl until well combined.
4. On a lightly floured surface, roll out one piece of the dough into a roughly 8- by 12-inch rectangle, 1/4 to 1/8 inch thick. Gently move the dough to the prepared baking sheet and put the whole thing in the fridge. Roll out the other piece of dough to roughly the same size, erring larger rather than smaller, and set it aside for a moment.
5. Remove the dough from the fridge and pour the blueberry mixture on top, leaving a generous border of at least 1 1/2 inches around the edges.
6. To make a lattice top, cut the remaining dough sheet into 1-inch strips and starting from the top left corner of the pie, lay one strip of dough horizontally and one strip vertically, so that the horizontal strip is on the bottom. Lay a second horizontal strip about 1/2 inch below the top strip so that it overlaps the vertical strip. Fold the top horizontal strip to the left and lay another vertical strip about 1/2 inch to the right of the first one. Next, fold the top horizontal strip back over it. This way, the second vertical strip will go underneath the top horizontal strip and over top of the second horizontal strip. Fold the first vertical strip up and lay down a third horizontal strip. Fold the vertical strip back down. Next, fold the second horizontal strip to the left and place a third vertical strip. Fold the horizontal strip back over the pie. Fold the middle vertical strip up and lay down the fourth horizontal strip. Fold the top and third horizontal strip to the left and place a fourth vertical strip. Continue until all strips are used and the top of the pie is covered. You may have to piece some scraps together to make the last few strips of dough. Fold the bottom crust up and over the top of the pie and press firmly with a fork to seal.
7. Alternately, do not cut the remaining dough into strips, but rather lay it over the blueberry filling in one piece, fold the bottom crust up over the top and seal the edges very well by pressing firmly with the tines of a fork, cut a few vents in the top and proceed with the recipe as follows.
8. Put the baking sheet into the refrigerator or freezer until the crust is very firm. When you are ready to bake, brush the top of the pie with a beaten egg and generously sprinkle it with sugar. Bake the pie until the crust is deep golden brown and the juices are bubbling, 35 to 45 minutes. Cool slightly before cutting into squares and serving with ice cream or whipped cream.
9. Note: Be prepared; a lattice-topped pie will probably leak, so do not forget to line your pan with parchment paper.