• Brown the beef and veal in a medium to large pot. Drain off fats, pour gravy into meat and turn down to a simmer.
• Make potato topping while meat simmers:
• Put oven rack in middle position and preheat oven to 400
• Wrap garlic in a double thickness of foil and seal well. Roast until very soft, about 45 minutes.
• While garlic roasts, peel potatoes and cut into 1-inch pieces. Cook in a 4- to 5-quart pot of boiling water, uncovered, until tender, about 10 minutes, then drain.
• Heat cream, milk, and butter in same pot over moderate heat, stirring occasionally, until butter is melted. Remove from heat and stir in salt and pepper.
• Unwrap garlic and cool slightly, then peel cloves. Force hot potatoes and garlic through ricer into hot cream mixture and stir to combine. Stir in cheese and keep warm, covered.

Make corn filling:

• Cook onions and garlic in oil in a 4- to 5-quart heavy pot over moderate heat, stirring occasionally, until golden, about 5 minutes. Add wine and boil, uncovered, until almost all of wine is evaporated, 10 to 15 minutes. Stir in cream, rosemary, salt, and pepper and simmer, uncovered, stirring occasionally, until mixture is reduced to about 1 1/2 cups, about 30 minutes. Add corn and simmer 5 minutes. Discard rosemary.

Assemble pie:

• Reduce oven temperature to 375
• Top meat filling with corn filling, then spread potato mixture on top and brush with egg. Put baking dish in a foil-lined shallow baking pan (to catch drips) and bake until fillings are bubbling and potato mixture is browned around edge, about 40 minutes. Let stand 10 minutes.