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.