Boil the lasagna noodles according to the package. Drain and dry, stretched out on some paper towels.

Remove the sausage from the casings and cook fully. Crumble the sausage up into a fine crumble as it is cooking. When it is fully cooked, remove from the pan and set aside.

Finely dice the onion, add two tablespoons of butter to the same skillet as the sausage was cooked in, you do not have to clean the pan in between. Fully cook the onions until they are soft and golden brown. Add salt and pepper to taste.While the onions cook, peel the potatoes cut into large, even chunks and boil in salted water until they are soft enough for mashing.

Drain and return the potatoes to the pan. Add 8 tablespoons of butter to the potatoes, the milk, and some salt and pepper to taste. Mash until creamy. Add the sour cream and the cooked onions. Add the sour cream a little at a time, you do not want the potatoes to be too runny. So eyeball this and add, you may not use all the sour cream. When you are done add 3 cups of the grated gouda to the potatoes and mix until melted and well combined.

Prepare a 9 x 12 casserole dish, spray some non-stick spray on bottom and sides or use butter or oil.

Spread the mashed potato mixture the entire length of every lasagna noodle and roll the noodles up with the potatoes inside, Nestle all the roll ups in the casserole dish. Some of the potatoes may leak out. This is ok. I used about 4 to 5 tablespoons of potatoes per noodle. My pan fit 12 to 13 roll ups, tightly packed into the casserole. I said to make extra noodles in case one or two tears.

Finally you make the sauce. In same pan as the sausage and onion, you do not have to clean the pan, add the remaining butter and all the mushrooms. Saute the mushrooms until golden brown and cooked. Add the sausage back to the pan with the mushrooms and cook for a few minutes. Then add the water and the bouillon. Simmer this on low for 20 minutes. Uncovered. At the 20 minute mark, whisk the corn starch into the half cup of water until dissolved. Slowly add to the simmering mushroom and sausage. Whisking the whole time. This should thicken into a gravy. Simmer and whisk on low for 10 minutes. Turn off heat. If you like you can add a little heavy cream to this too.

Pour this over the roll ups in the casserole dish.

Top the whole dish with the remaining gouda cheese, and some dried parsley and black pepper.

Cover the dish with foil. Bake at 350° for 30 minutes. Uncover and bake for a few minutes until the cheese is bubbly and brown.

Serve immediately or it can be reheated.