In a large bowl or pot, soak the sweetbreads in cold water for 2 hours in order to clean them.
In a large pot add the salted water and bring to a boil. Add the potatoes and cook until tender, about 20 minutes. Once the potatoes are cooked remove from the water and coarsely mash together to make about 2 cups. Set aside.
Once the sweetbreads are clean place them in a medium pot with the salted water and poach them for 20 to 25 minutes over medium-high heat. Remove the sweetbreads from the pot and press them between 2 pans with weight on top. Place the sweetbreads in the refrigerator and chill completely.
After the sweetbreads are chilled cut them into 1/2-inch slices. Season the sweetbreads with salt, and pepper, to taste and set aside.
In a medium saute pan add 2 tablespoons of olive oil and warm over medium-high heat. When the oil is hot add the bacon and cook until golden brown, about 3 minutes. Add the garlic and the paprika and cook together for another 30 seconds. Add the apple cider vinegar to the pan and stir together. Add the mashed potatoes and saute for 1 minute. Season the potatoes with salt, and pepper, to taste. Turn off the heat, add the scallions and stir to combine. Keep warm until ready to serve.
In a medium saute pan heat the remaining olive oil over medium heat. Add the chilled sweetbreads and pan-fry until the sweetbreads are crispy on both sides, about 4 minutes on each side.
To serve: Spoon the potato hash into the center of each serving plate. Lay the sweetbreads over the potatoes and garnish with the lemon wedges and fresh herbs, if using.