How to Make It
Prepare the French Toast: Arrange bread slices in an 11- x 7-inch glass baking dish coated with cooking spray. Beat together cream cheese and brown sugar in a bowl with an electric mixer on medium speed until smooth, 3 to 4 minutes. Reduce to medium-low speed, and add eggs and egg whites, one at a time, beating well after each addition. Add milk, vanilla, and salt; beating at low speed until completely combined. Pour mixture over bread slices. Cover and refrigerate overnight.
Prepare the Streusel: Preheat oven to 350°F. Stir together oats, sugar, flour, and salt. Add butter, and use your fingers to combine mixture until crumbly. Stir in nuts. Sprinkle Streusel over soaked bread slices. Bake until golden brown and eggs are set, 20 to 25 minutes. Remove from oven, and let stand 5 minutes.
Prepare the Topping: Whisk together yogurt, milk, powdered sugar, and vanilla in a small bowl until smooth. Drizzle Topping over casserole. Top with berries, and serve immediately.