Preheat oven to 350°F.
Place cubed bread on a baking sheet and place in the oven to dry out while preparing the remaining ingredients.
Whisk together the eggs, cream, milk, vanilla, salt and sugar. Continue until the sugar is dissolved. Spread the bread into a casserole dish, 9 X 13 if you want a single layered bread pudding or 9 X 9 if you prefer a thicker bread pudding with a crunchy top. Pour in the milk mixture. Gently stir in the rhubarb and white chocolate.
Bake until set, about 1 hour. Remove from oven and let stand 15 min before serving.
Can also be served cold.