Wash the potatoes and poke with a fork. Bake for 45- 60 minutes at 350 degrees Fahrenheit before peeling and shaving/ricing into a bowl.
Once cool, add the egg, flour and seasoning and gently mix until the dough is formed. Allow to rest for up to 10 minutes.
Flour a work surface and roll out the dough into logs. Cut into inch sized cylinders and press gently with a fork. Boil these gnocchi in salted water until they rise to the top.
For the sauce, melt the butter and flour until a roux forms. GENTLY add the water until a lump free sauce is achieved. Season with salt and pepper and mix in the grated cheddar and blue cheese until fully incorporated.