Bring 6 quarts water to boil and add 2 tablespoons of salt.
Pinch off walnut-sized balls of the gnocchi dough and roll with a rolling pin to form 2 1/2-inch circle of dough. Place 1/4 of a plum and a 1/2 teaspoon sugar on each and fold dough around plum pieces to form a package without tears or rips, relatively smooth and evenly coated. Continue until all are finished.
Place the gnocchi in the water, 10 at a time, and carefully stir to prevent sticking to sides or bottom of pan. Allow to float and continue cooking for 2 minutes. Meanwhile, melt the butter in a 12-inch saute pan over medium heat. Add the bread crumbs and then add cooked gnocchi and toss gently to coat. Serve on a plate and sprinkle with cinnamon.
Basic Gnocchi Dough:
3 pounds russet potatoes
2 cups all-purpose flour
1 egg, extra large
1 pinch salt
1/2 cup canola oil
Boil the whole potatoes until they are soft (about 45 minutes). While still warm, peel and pass through vegetable mill onto clean pasta board.
Set 6 quarts of water to boil in a large spaghetti pot. Set up ice bath with 6 cups ice and 6 cups water near boiling water.
Make well in center of potatoes and sprinkle all over with flour, using all the flour. Place egg and salt in center of well and using a fork, stir into flour and potatoes, just like making normal pasta. Once egg is mixed in, bring dough together, kneading gently until a ball is formed. Knead gently another 4 minutes until ball is dry to touch.