Step 1

Combine garlic, hoisin, brown sugar, honey, wine, soy sauce, salt, five-spice powder, oil, pepper, and food coloring (if using) in a large baking dish or 2-gal. resealable plastic freezer bag. Add pork loin to marinade and turn to coat. Cover baking dish with plastic wrap or seal bag. Chill, turning loin a few times, at least 4 hours and up to 12 hours.

Step 2

Working in 2 batches, pulse shallot, garlic, mushrooms, and cilantro in a food processor just until finely chopped (do not overprocess).

Step 3

Heat oil in a large skillet over medium. Cook mushroom mixture, stirring occasionally, until mushrooms have started to brown and pan is almost dry, 5–7 minutes. Pour in wine and reduce heat to low. Cook, stirring once or twice, until pan is dry, 10–15 minutes. Season with salt and pepper. Transfer duxelles to a medium bowl and chill until cold, at least 30 minutes.Do Ahead: Duxelles can be made 2 days ahead. Transfer to an airtight container; cover and chill.

Step 4

Remove loin from fridge and let sit at room temperature 1 hour.

Step 5

Place a rack in middle of oven; preheat to 400°. Remove loin from marinade and pat dry with paper towels. Strain marinade through a fine-mesh sieve into a small bowl and chill until ready to use. Place loin, fat side up, on a foil-lined rimmed baking sheet and roast 30 minutes. Let cool. If loin is tied, remove twine.

Step 6

Dust a work surface lightly with flour and unfold both sheets of puff pastry on surface. Arrange sheets side by side, with long sides facing you and short sides overlapping slightly. Press short sides together with your fingers or a rolling pin to seal and form one long rectangle. Dust pastry with flour, then roll out to large enough to encase loin.

Step 7

Spread duxelles over center of pastry to create a rectangle about the length of loin, leaving a 1" border at top and bottom. Lay prosciutto slices, overlapping slightly, across duxelles. Place loin on top of prosciutto. Starting with edge closest to you, roll up pastry, letting top and bottom edges overlap slightly; trim any excess, then pinch edges together to seal. Turn Wellington seam side down and twist ends to seal. Trim any excess pastry from sides, but make sure loin is completely encased in pastry. Transfer Wellington to a rimmed baking sheet and chill until pastry is firm, about 1 hour.

Step 8

Preheat oven to 400°. Lightly brush pastry all over with egg. Using a sharp paring knife, cut 3 diagonal slits in pastry across top of Wellington to let steam escape (do not cut all the way down into the meat). Sprinkle Wellington with sea salt.

Step 9

Bake Wellington until pastry is deep golden brown all over and an instant-read thermometer inserted into the center registers 145° (the temperature will climb as Wellington rests), 30–40 minutes. Transfer to a wire rack set inside a rimmed baking sheet and let rest 15 minutes.

Step 10

Meanwhile, melt butter in a medium skillet over medium heat. Whisk in 2 Tbsp. flour and cook until mixture is golden brown, about 2 minutes. Pour in broth and cook, whisking often, until thickened, about 3 minutes. Add reserved marinade and reduce heat to medium-low. Simmer, whisking occasionally, until gravy is slightly thickened, about 5 minutes.

Step 11

Transfer Wellington to a platter and arrange cilantro around. Cut into thick slices and serve with gravy alongside for pouring over.Do Ahead: Wellington can be assembled 1 day ahead; cover with foil and chill. Let sit at room temperature 30–40 minutes before baking.