For the hollandaise: Melt the butter in a small saucepan over medium-high heat or in the microwave. Combine the yolks, sage, lemon juice, salt and pepper in a food processor or blender and pulse to incorporate. Carefully drizzle the hot butter into the processor and keep blending until the sauce is thick and creamy. Pour the sauce into a small bowl and set aside.
For the stuffing cakes: Place the stuffing in a large bowl, breaking up any large clumps. Add the eggs and breadcrumbs and stir to combine, making sure all of the stuffing is evenly coated with the eggs. Scoop 1/3 cup of the stuffing into your hands and shape into a patty, about 3-inches wide and 1/2-inch thick. Repeat to make 6 stuffing cakes. Heat the oil in a medium skillet over medium-high heat and cook the cakes, two at a time until golden brown, 2 to 3 minutes per side. Transfer to a paper-towel-lined plate and repeat with the remaining cakes. Loosely cover with foil to keep the cakes warm.
Place a large nonstick skillet over medium-high heat and cook the pancetta until browned and crispy, about 4 minutes on each side. Transfer to a paper-towel-lined plate.
To assemble, fill a small saucepan with 3 inches of water, and add the lemon juice and salt. Bring the water to a simmer over medium heat. Crack an egg into a small heatproof bowl and use the bowl to slowly slide the egg into the water. Use a wooden spoon to carefully stir the water around the egg. Cook the egg until the white has set and the yolk is still soft, 2 to 2 1/2 minutes. Remove the egg from the water with a slotted spoon and drain it on a paper-towel-lined plate. Repeat with the remaining eggs. To serve, place one stuffing cake on a plate. Top with 2 slices of pancetta, a poached egg and a generous drizzle of hollandaise sauce.