Place the spinach in a sieve or strainer, leave to thaw and drain if using frozen or drain if using canned.
Heat 1 tablespoon oil in a large skillet over medium heat, add the onion and garlic, fry for about 5 min or until lightly browned. Add the veal and fry for 1o min or until browned, stirring constantly. Stir in the mushrooms, tomato paste, sugar, and oregano. Add salt and pepper to taste, stir well to combine. Add beef stock or water, cover pan and continue cooking for 10 min, stirring occasionally. Remove from heat and stir in egg. Set aside.
Cook chosen pasta per package directions until soft, drain, and toss gently with 1 tablespoons oil. Set aside
In a small, heavy saucepan, melt 4 tablespoons of butter over low heat. Blend 4 tablespoons of flour into the melted butter. Cook over low heat, stirring, for 4 to 5 minutes. Slowly add 2 cusp of milk, stirring constantly. Continue cooking slowly until smooth and thickened. Stir in the spinach and the parmesan cheese. Simmer until cheese melts, stirring constantly. Salt and pepper to taste, then beat in 1 tablespoon of butter.
Preheat oven to 350º. Grease a shallow baking dish. Spoon the veal-mushroom filling into the cooked pasta. Place in the baking dish. Spoon over the spinach and cheese sauce and bake in oven for 15-20 min or until sauce is bubbling.