In a large bowl, whisk together the eggs, milk, maple syrup, vanilla and salt. In a small dish, stir together the cream cheese and sugar.
Cut or tear the bread into cubes into a buttered casserole dish, stopping halfway to add a few dollops of the cream cheese mixture and a handful of blueberries. Add the rest of the bread and scatter with blueberries. Top with blops of the remaining cream cheese.
Pour the egg mixture evenly overtop; cover with plastic wrap and refrigerate for 6 hours, or overnight. Meanwhile, make the blueberry sauce: In a small saucepan, stir together the sugar and cornstarch until there are no more lumps. Add 1/2 cup water and bring to a simmer; cook, stirring constantly, until the mixture thickens and bubbles. Continue to cook for a few more minutes, until the berries burst.
Remove from the fridge about 30 minutes before baking, as you preheat the oven to 350F. Bake for 30 minutes, until golden and set. Let sit for a few minutes before serving warm, with blueberry sauce or maple syrup. Serves 6.
Serving Size Serves 8.