Heat butter and oil in large skillet over med.-high heat. When butter foams, add onion, carrot, celery, cook, stirring until veggies lightly golden and soft, 4-5 minute
Add veal and pancetta, cook, stirring, until meat lightly colored, 5-6 minute.
Raise heat to high and add wine. Cook until wine almost all reduced, 3-4 minute
Add tomatoes and broth, and season with salt and pepper. Bring sauce to boil. Reduce heat to low and cover skillet with lid slightly askew. Cook 1 to 1-1/2 hours, or until sauce has med.-thick consistency. Stir a few times during cooking.
Heat milk in small saucepan over low heat.
Melt butter in medium saucepan over med.-low heat. When butter foams, add flour and stir 2-3 minute without letting flour turn brown.
Add milk to butter all at once and mix quickly. Season with salt and cook, mixing constantly, until sauce has med.-thick consistency and is smooth and velvety, 3-5 minute (If too thick add bit more milk).
Remove from heat, cover pan, refrigerate until ready to use.
Preheat oven 400°F Generously butter large deep baking dish.
Bring large pot of water to boil. Add salt and Rigatoni. Cook, uncovered, until tender, but firm to bite. Drain pasta and place in large bowl.
Add meat sauce, 1 cup béchamel and 1/3 cup cheese. Mix thoroughly and place in baking dish. Top with Béchamel and sprinkle cheese over top, dot with butter.
Bake 10-15 min., or until cheese melted and pasta nice golden color.
Meat sauce day ahead. Reheat when ready to use.
Béchamel few hours ahead.
Pasta cooked and assembled with sauces one hour ahead.