In an 8x8 baking dish, whisk eggs with milk, sugar, lemon zest, cinnamon and vanilla. Dip croissants into mixture to soak up liquid. Cover with plastic wrap and refrigerate for one hour.

Preheat oven to 350F. Remove plastic wrap from dish and bake for 45-50 minutes.

Serve with icing sugar, maple syrup and blueberries.