Preheat oven to 350 degrees. Place croissant pieces into a greased 8x8 square pan {or similarly sized casserole dish}. Sprinkle with fresh or defrosted blueberries.

Beat cream cheese, sugar, eggs and vanilla in medium bowl with electric mixer until well blended. Gradually add milk, beating well after each addition. Pour evenly over croissant pieces. Let stand 20 minutes {you can also cover and refrigerate the dish leaving it overnight to bake in the morning}.

Just prior to baking, prepare optional topping by combining brown sugar and flour in a small bowl. Using a pastry cutter or your fingers, incorporate cold butter into the mixture until it resembles coarse crumbs. Sprinkle over the top.

Bake at 350°F for 35 to 40 minutes or until set in center and golden brown. {You may want to cover it with foil for the last 10 minutes if the tops are getting too brown.}

Serve warm.

Variation: Instead of baking in a square pan, you can also bake individually. Place croissant pieces evenly in 8-10 {1/2-cup} ramekins; sprinkle with blueberries and pour cream cheese mixture evenly over croissant pieces. Let stand for at least 20 minutes. Sprinkle each with topping mixture {optional}. Bake at 350°F for 20 to 25 minutes or until set in center and golden brown.