Bake the potatoes at 350 until tender, about an hour and a half.
Remove the skin from the potatoes. Use a potato ricer to break up the potatoes into a bowl. Stir in the butter and cream. Add more milk or cream if needed to soften. Taste and season with salt and pepper to taste.
Cook the bacon about 8 minutes until mostly cooked. Add the sausage and cook another 8 minutes until just about fully cooked and lightly browned. Add the onion and cook another 5 minutes.
Add the two tablespoons of butter to the pan along with the flour. Stir well to combine and continue to stir and cook for 3 minutes until the flour is fully mixed in and the color darkens by a shade or two.
Whisk in the milk and the parsley and bring to a simmer. Cook for 2 minutes until the sauce is thickened. Pour into the baking dish.
Turn oven to 375
Crack the eggs into a bowl and beat until smooth. Add salt and pepper. Cook in a nonstick pan, stirring constantly, until mostly set but still pretty runny. Pour this mixture over the sausage.
Use a piping bag or the corner of a large zip lock bag to pipe the potatoes onto the top of the casserole. Top with the cheese.
375 for 30 minutes. Remove from oven and allow to cool for 10 minutes before serving.
