Gnocchi with Creamy Brie Sauce

for the gnocchi:
2 russet potatoes
coarse salt, for sprinkling
3 egg yolks
1/2 cup Parmesan cheese, shredded
1/4 tsp nutmeg
1/2 tsp salt
1/4 tsp pepper
1 cup flour, plus more for dusting

for the sauce:
2 tbsp butter
3 tbsp flour
1 cup milk
3 oz brie, cut into small pieces
1/4 cup mozzarella cheese, shredded
1/4 cup Parmesan cheese, shredded
1/2 tsp garlic powder
1/4 tsp Italian seasoning
parsley, for garnish

Preheat oven to 425.
Sprinkle a baking sheet with coarse salt and arrange the potatoes on top.
Bake at 425 for about 45 minutes, or until slightly overcooked. 
Let the potatoes stand until cool enough to handle, or about 10 minutes. 
Slice the potatoes in half and remove the skin, leaving the potato intact.
Grate the potatoes into a bowl using the large holes of a cheese grater. 
Place the potatoes in a mound on a flat surface, leaving a well in the center.
Add the egg yolks, cheese, nutmeg, salt, and pepper in the center of the mound.
Mix the ingredients together by hand until well combined.
Sprinkle 1/2 cup flour over the potato mixture, pressing the flour into the mixture with your knuckles. Fold the mixture over on itself, add more flour, and repeat, adding more flour as necessary until the mixture is firm, but still gives until slight pressure. Continue to add more flour if the mixture is too wet. To test if you have the right consistency, you can break off a small piece of dough and roll it into a rope, 1/2 inch in diameter. If the rope holds its shape, it should be right. If it does not, add more flour and test again as necessary. 
Keeping the work surface well-floured, divide the dough into four equal pieces. 
One at a time, roll each of the four balls into a rope, 1/2 inch in diameter, keeping the rope well-floured as you go.
Cut the rope into small, equal pieces, keeping them floured as you go.
Roll each piece down the tines of a fork to get the classic gnocchi shape.
Move the pieces to a foil-lined baking sheet and repeat with the remaining three pieces of dough.
Once you have finished with all the dough, set the gnocchi aside to rest for 30 minutes. 
Melt the butter in a large pan over low-medium heat.
Once the butter has melted, add in the flour, whisking constantly until the flour is incorporated.
Add in the milk, all three cheeses, and garlic powder.
Whisk until smooth, then add in the Italian seasoning. Keep the sauce over low heat, stirring occasionally until ready to serve.
Bring a pot of water to a boil, then drop in the gnocchi, about 10 at a time. Allow to boil for 90 seconds after the gnocchi rises to the top of the water.
After the 90 seconds, remove with a slotted spoon and then drain.
Top with the brie sauce, and garnish with parsley.