For the Hash:

1. Preheat oven to 350°F.
2. In a large skillet over medium heat, cook the bacon, stirring, until crispy. Reduce flame to medium-low; add the onion and celery, and cook, stirring, for another 8 minutes, until golden brown and tender. Add the turkey, Brussels sprouts, chestnuts, and cayenne pepper, toss to combine. Push ingredients to one side of pan, remove from heat and add bourbon to bare side of pan. Return pan to the stove, tilting to allow the bourbon to catch flame. Toss until the flames subside. Add 1/2 cup gravy, chopped herbs and season to taste.
3. Divide potatoes among four small oven proof gratin dishes and spread evenly in bottom of each dish. Arrange the hash on top of each, packing it down. Transfer to oven and bake for 15 minutes. Meanwhile, poach the eggs.

For the Poached Eggs:

1. Fill 1/3 of a large saucepan with water and bring to a simmer. Add pinch of salt & white vinegar (which helps the whites to coagulate.) Stir the water a little bit to create a vortex and crack an egg into the center. This helps the white stay centered around the yolk. Repeat for each egg. Poach the eggs to the desired degree of doneness (2-4 minutes for soft poach).
2. To serve, gently place a poached egg on each turkey hash. Sprinkle with chives, salt and pepper, and drizzle remaining gravy around. If using, garnish the top with watercress salad.