Peel the onion and cut it into thin strips

Cut the bread into very small pieces.

In a separate bowl, whisk together the egg with the mustard, milk, and cream. Add the ground nutmeg and season with salt and freshly ground pepper.

Heat the clarified butter in a large skillet. Add the rolled up sausage and brown on both sides, about 2 minutes for each side.

Carefully remove the sausage from the pan and set it aside. Try to keep it all in one piece without breaking.

Add the onion pieces to the pan with the sausage drippings and cook until transparent, stirring frequently.

Sprinkle the tablespoon of white granulated sugar over the onions and cook for another few minutes until they become light brown and start to caramelize.

Mix in the sauerkraut until everything is evenly combined. Season with salt and freshly ground pepper to taste.

Preheat the oven to 350 degrees F.

Grease and flour a 9-inch tart pan. Press the bread pieces into the prepared tart form to create a crust.

Spread the sauerkraut caramelized onion mixture evenly into the bread shell.

Lay the curled up chicken sausage on top of the sauerkraut mixture making sure the sausage is tucked away from the edges of the bread crust. It should not be hanging over the sides.

Spread the creamy egg mixture evenly over the top of the sausage.

Place the pan in the oven and bake for 45 minutes.

Remove from oven and let stand 15 minutes before removing the tart from the pan.

Transfer to a wire rack and let cool another 15 minutes before transferring to a serving plate.

Slice and serve.