For the potatoes: Preheat the oven to 400 degrees F.
Make a bed of salt on a quarter-sheet tray and place the potatoes on top. Bake until tender, about 1 hour. Slice the potatoes in half lengthwise, then hollow out the skins, scooping the flesh into a bowl. Add the cream, butter, egg yolks and cheese to the potato filling and mix thoroughly.
For the pork belly: Meanwhile, turn the heat under a large stovetop pressure cooker to medium-high and add 2 tablespoons oil, along with the onions and garlic. Allow to sweat, about 3 minutes. Add the juniper, allspice, clove, mustard seeds, peppercorns and bay leaves and stir to combine. Pour in the beer and stir in the soy sauce and brown sugar. Bring to a simmer, then gently add the pork belly. Carefully secure the pressure cooker lid and bring to high pressure over medium-high heat. Cook at pressure for as long as it takes for the potatoes to cook, 45 minutes to 1 hour. Turn off the heat and carefully run the pressure cooker under cold water until cool enough to open. Open and remove the pork.
Preheat a deep-fryer or a large Dutch oven with oil to 350 degrees F.
Set aside some of the pork pieces for garnish, glazing with what is left in the pressure cooker. Fry the pieces in batches until crispy, 2 to 3 minutes.
Chop the crispy fried pork into chunks, then fold them into the potato mixture. Spoon the potato mixture into the potato skins and bake until crispy and browned, about 15 minutes. Top each with any remaining pork belly pieces and green onions.