Preheat oven to 200 degrees F.
Chop all the potatoes except two into large cubes of about the same size. Place them in a large saucepan, generously season with salt and add cold water so potatoes are covered by approximately 1 inch. Bring to a boil over high heat, reducing heat to low and continuing to simmer until potatoes are fork tender (but not dissolving and saturated).
Meanwhile, grate the remaining two potatoes on the large holes of a box grater. Transfer to a fine mesh strainer over a medium bowl and sprinkle with 1/4 teaspoon salt. Allow the potatoes to drain their liquid as the potatoes boil. Set aside.
Prepare the remaining ingredients. Grate the corned beef and chop the fresh chives. In a medium mixing bowl whisk together the eggs, 1/2 cup milk, flour and salt + pepper. Add the chopped chives and corned beef and stir until just incorporated.
When the boiling potatoes are ready, drain and return to the same pot. Add 1/4 cup milk and mash the potatoes until smooth. Use a rubber spatula (or your clean hands) and press the grated potatoes against the sides and bottom of the mesh strainer to remove as much liquid as possible. Transfer to the mashed potatoes and combine.
To the mashed potatoes add the egg and corned beef mixture. Gently stir until evenly incorporated.
Heat a large skillet or griddle over medium heat. When pan is hot enough (test this by sprinkling a drop or two of water on the skillet; it is bounces off, the pan is ready. If it evaporates instantly, it's too hot). Add 1-2 tablespoons of butter to the skillet and swirl to completely coat the bottom. Fill a 1/3 cup measuring cup with batter and drop it onto your skillet, using a rubber spatula to gently spread out the batter so that each pancake is approximately 1/4 inch thick. Repeat this process filling your skillet (but leaving space between each pancake).
Cook each pancake for approximately 4-5 minutes on each side, or until fully cooked and nicely golden brown. Transfer to a baking sheet or cooling rack to keep warm in the oven until remaining pancakes are ready.
Serve with sour cream, Thousand Island dressing and fresh chives.