Grease bottom and sides of 9x13 inch pan glass baking dish with butter. In large bowl, beat flour, half and half, 1/4 cup sugar, the vanilla, salt, and eggs with wire whisk until smooth. Stir in bread and 1.5 cups mixed berries. Spoon into the baking dish. Cover tightly and refrigerate for atleast 1 hour but no more than 24 hours. Heat oven to 400 degrees. Uncover pan. Bake 25 - 35 minutes until golden brown. Meanwhile, stir together sugar and corn starch. Stir in orange juice until smooth. Stir in 1 cup mixed berries; heat to boiling over medium heat, stirring constantly until slightly thickened. Remove from heat. Stir in strawberry halves just before serving. Serve warm over french toast bake.