"Impossible" Ham & Cheese Pie

Never heard of an impossible pie? The lure of this 1970s phenomenon is that you get a "crust" without rolling out pie dough. Traditionally, Bisquick batter was poured over vegetables, meat, and cheese and baked. To prevent the "crust" from sticking to the pan, you should coat the buttered dish with Parmesan cheese, which makes for a crispy, well-browned (not to mention tasty) exterior. Replace the Bisquick with a simple batter of flour, baking powder, eggs, and milk, which you then pour over a no-cook mixture of Gruyère cheese, ham, and scallion. Use a rasp-style grater or the smallest holes on a box grater for the Parmesan. 

1 tablespoon butter, softened, PLUS   
   2 tablespoons butter, melted
3 tablespoons finely grated Parmesan cheese
8 ounces Gruyère cheese, shredded
4 ounces thickly sliced deli ham, chopped  
4 scallions, minced  
1/2 cup all-purpose flour
3/4 teaspoon baking powder
1 cup half-and-half  
4 large eggs, lightly beaten  
2 teaspoons Dijon mustard  
1/8 teaspoon ground nutmeg

Adjust oven rack to lowest position and heat oven to 350°F. Grease 9-inch pie plate with softened butter, then coat plate evenly with Parmesan.

Combine Gruyère, ham, and scallions in bowl. Sprinkle cheese-and-ham mixture evenly in bottom of prepared pie dish. Combine flour, baking powder, pepper, and salt in now-empty bowl. Whisk in half-and-half, eggs, melted butter, mustard, and nutmeg until smooth. Slowly pour batter over cheese-and-ham mixture in pie dish.

Bake until pie is light golden brown and filling is set, 30 to 35 minutes. Let cool on wire rack for 15 minutes. Slice into wedges. Serve warm.