In a large bowl, use a fork to combine flours, sugar, and sea salt. Grate in butter and massage into flour with fingertips until it has a uniform, crumbly texture. Fold in vodka and then just enough ice water for dough to hold together when pinched.

Turn out onto a lightly floured surface, gather into a disc, and wrap tightly with plastic. Chill 30 - 60 minutes. For airier dough, roll dough into a rough 8 x 15-inch rectangle, fold inward into thirds, and then roll envelope just enough to hold together, rewrap dough, and chill for 30 minutes or longer. Repeat 3 times. (More on the technique here.)

Preheat oven to 425 degrees F. If desired, line a rimmed baking sheet with parchment.

In a large mixing bowl, toss to combine pears, sugar, lemon zest, nutmeg, and sea salt. For a prettier presentation, gather the pears into groups in graduated sizes as you place them in the galette. (See 'Assembling the Galette' above for more info!)

On a lightly floured surface, roll chilled dough into an 11 x 14-inch rectangle. Set on prepared baking sheet. In the center of dough, spread jam into a 5 x 8-inch rectangle. Gather pears side-by-side and arrange within the jam rectangle. Fold up the sides around the filling, crimping the dough as you go. Brush crust with egg wash and sprinkle with sugar.

Cool 2 hours, slice, and serve.