How to Make It
In a shallow dish, mix the salt with the sugar; add the pork belly and coat with the mixture. Cover the pork and refrigerate overnight.
The next day, rinse the pork belly and pat dry. Preheat the oven to 300°. In an ovenproof skillet, heat the oil until shimmering. Add the pork and cook over moderate heat, turning once, until richly browned, 3 minutes per side. Add the broth, thyme, shallot, carrot and celery and bring to a boil. Cover and braise in the oven until the pork is tender, 2 hours. Transfer the pork to a plate, cover with foil and keep warm. Boil the cooking liquid until reduced by two-thirds, 15 minutes. Strain the liquid into a saucepan and skim off the fat.
In a bowl, combine the flours with the nutmeg, 1 teaspoon of salt and 1/2 teaspoon of pepper. In a medium bowl, whisk the eggs with the milk, then whisk the mixture into the flours. Cover the batter and let rest at room temperature for 30 minutes.
Bring a large pot of salted water to a boil. Prepare a bowl of ice water. Carefully hold a colander with large holes over the boiling water. Gradually add the batter to the colander and press it through the holes with a spatula. Boil the spaetzle until tender, 1 minute. Using a slotted spoon, transfer the spaetzle to the ice water to cool completely, then drain on paper towels.
In a large nonstick skillet, melt the butter in the olive oil. Add the spaetzle and cook over high heat until browned on the bottom, 2 minutes. Stir and cook until browned all over, 1 minute longer. Season with salt and pepper and keep warm.
In a large, deep skillet, heat the olive oil. Add the garlic and onion and cook over moderate heat, stirring occasionally, until beginning to brown, about 7 minutes. Add the thyme and cook for 1 minute. Add the chicken broth and collards and bring to a boil. Cover and simmer over low heat, stirring occasionally, until the collards are tender, about 10 minutes. Season with salt and pepper.
Slice the pork lengthwise and transfer to plates. Spoon the greens and spaetzle alongside. Pour the reduced pork cooking liquid over the meat and serve.