Place the bread cubes in a lightly greased 9x13-inch casserole dish.
In a blender, mix the silken tofu, coconut milk, cornstarch, granulated sugar, brown sugar, vanilla extract, cinnamon, and salt until smooth and creamy.
Evenly distribute the custard over the bread cubes. Lightly press the bread to help the liquid absorb. Then, cover and refrigerate for a minimum of 2 hours or overnight.
Set your oven to preheat at 350°F. In a small bowl, combine brown sugar, cinnamon, all-purpose flour, and cold vegan butter, using your fingers or a fork to achieve a crumbly texture. Evenly distribute the topping over the soaked bread.
Bake uncovered for 45 minutes until the top is golden and the custard is set. If desired, broil for 2-3 minutes at the end of baking to brown the top more. Optional: Dust lightly with powdered sugar and serve with warm maple syrup or fresh fruit.