1 package frozen chopped spinach — (10-oz.) thawed
1 package mezze penne pasta — (16-oz.)
2 1/2 tablespoons butter
3 large shallots — sliced
2 tablespoons all-purpose flour
1 1/2 cups half-and-half
1/2 cup ricotta cheese
1 cup freshly shredded Asiago cheese — (4 oz.) divided
10 large eggs — lightly beaten
1/3 cup loosely packed fresh flat-leaf parsley leaves — coarsely chopped
1 tablespoon finely chopped chives
2 teaspoons kosher salt
1 teaspoon freshly ground pepper
Garnishes: fresh flat-leaf parsley leaves — shaved Parmesan cheese
Preheat oven to 325°. Drain spinach well, pressing between paper towels.
Prepare pasta according to package directions.
Meanwhile, melt butter in a medium saucepan over medium heat; add shallots, and sauté 5 minutes or until golden brown. Whisk in flour until smooth; cook 1 minute, whisking constantly. Gradually whisk in half-and-half; cook over medium heat, whisking constantly, until thickened and bubbly. Whisk in ricotta and 1/2 cup Asiago cheese until smooth. Remove from heat.
Whisk eggs in a bowl until frothy. Fold in shallot mixture, spinach, parsley, and next 3 ingredients. Stir in cooked pasta.
Sprinkle 1/4 cup Asiago cheese on inside rim of a lightly greased 9-inch springform pan. Pour pasta mixture into pan.
Bake at 325° for 55 minutes to 1 hour and 10 minutes or until set. Let stand 10 minutes. Remove sides of pan. Sprinkle with remaining 1/4 cup Asiago cheese.