Prepping the sweetbreads (de-salting): As soon as you buy the sweetbreads, cover with about 1 quart cold water and store in the refrigerator overnight, changing the water as often as possible. The next day, rinse the sweetbreads, place them in a pot and cover with water. Bring to a boil, add salt and simmer for 5 minutes. Drain the water. Rinse them and transfer to an ice bath. Pat dry and store in the refrigerator, wrapped in a towel, pressed with a heavy weight to remove any excess moisture.
Rehydrating the morels: Soak the mushrooms in warm milk for 30 minutes. Drain and reserve the liquid. Wrap the morels in paper towels and store in a bowl in the refrigerator until ready to use. Strain the liquid through a fine mesh sieve and set aside.
Cooking the sweetbreads:
Season the turkey with pepper. Sprinkle with ½ tablespoon flour.
Chop the morels and button mushrooms.
In a non-stick pan, heat the oil. Add the shallots and fry until lightly golden. Add the ground turkey and stir-fry for 2 minutes. Add the mushrooms and cook for 4-5 minutes. Transfer to a plate.
In the same pan, add more oil if necessary. Add the bouquet garni and the sweetbreads. Season with white pepper. Cook for 4-5 minutes, then flip them and cook for another 2-3 minutes. Add the turkey stock, bring to a boil, then add the reserved warm milk. Bring to a boil one more time, then let simmer for 5 minutes.
Remove the sweetbreads from the liquid and set aside, discarding the bouquet garni. Remove any membrane, if any. Add capers. Toss well and reserve.
Strain the liquid through a fine mesh sieve and let sit for 15-30 minutes. Remove and discard the fatty part that rises to the surface and reserve the remaining liquid.
For the cream:
In a mixing bowl, whisk the egg yolk with sugar until pale; the texture of the egg yolk will be thicker.
Warm the reserved liquid from the sweetbreads.
In a saucepan, melt 4 tablespoons butter over medium-low; you don't want the butter to burn. Add flour. Keep stirring manually with a whisk for approximately 3 minutes until well-incorporated. Add the warm liquid in 3 stages, then add the crème fraîche. Stir well.
Pour in some of the crème fraîche mixture slowly to the egg yolk so that the egg doesn't curdle. Transfer the egg mixture to the saucepan and reduce the heat to low. Season with pepper. Add the ground turkey, shallots, mushrooms and sweetbreads. Turn off the heat, cover and let rest until it's time to assemble the dish.
Forming the pastry shells:
Preheat the oven to 350°F.
Melt 2 tablespoons of butter. Add 1 tablespoon oil and stir well.
I used scalloped-edge cookie cutters. Cut the puff pastry dough into 3"-diameter rounds. Reserve 4 rounds. Using a smaller-sized cookie cutter, cut out 1½"-diameter holes in the center of the 12 remaining rounds. Reserve the mini-disks as well (they'll be used a topping for the pastries).
Lay the large and small rounds out on a silicone mat lined baking sheet. Prick the dough using a fork 3-4 times to let some of the steam out as they bake.
Place the 4 large rounds onto a baking sheet lined with parchment paper. Brush a thin layer of butter/oil using a silicone brush at the edge of the rounds and on the rest of the hollowed rounds. Super-impose a large round (as the base of the pastry) with a hollowed round on top on the baking sheet. Top with the last layer of puff pastry dough. Place it in the freezer for about 15 minutes. Prick the dough with a fork.
Bake for 11 minutes at 350°F. The texture of the puff pastry should be very flaky.
Allow to cool completely.
When you're ready to serve, spoon the sweetbread filling into the pastry. Cover the bouchée à la reine with a small puff pastry disk.
Sprinkle with parsley.
I used 2 different sizes of cookie cutters to create the pastry shells: 3" scalloped-edge and 1-½" cookie cutters. You could use any other shape or size you have on hand or simply use the rim of a glass.
I asked my cousin, who was visiting San Francisco (I don't go to SF very often even though I live a few minutes away by train), to buy sweetbreads for me. You can sometimes find some at Falletti Foods on Broderick street or at most meat shops in the Ferry Plaza. I also found some years ago at Andronico's.
I used leftover turkey stock from Thanksgiving.
I used store-bought Pillsbury crescent rolls for the puff pastry as I didn't have time to make my own.
Little reminder on how to make a bouquet garni: The traditional bouquet garni is composed of a sprig of thyme, 2 bay leaves (torn in half), 1 small portion of leek (only the green part), a few curly parsley stems and a small stalk of celery. You can always tweak it by substituting some of your favorite ingredients. Gather all the ingredients in a square of cheesecloth and tie it with some string or twine. You can use it to flavor sauces and broths.