Preheat oven to 300 degrees. Trim the crust from the bread and cut into bite-sized cubes and transfer to a baking sheet. Drizzle the olive oil and 1/2 teaspoon truffle salt over the bread. Toss with your hands until the bread is lightly coated. Bake for 15-20 minutes until lightly brown and crisp. Set aside.
Bring a medium pot of salted water to a boil. Cut the broccoli florets from the stems. Peel the stems using a vegetable peeler and trim the woody part of the stalk (roughly the last inch). Cut the stalks into 1/2" planks so they cook at the same pace as the florets.
When the water comes to a boil add the stalks and stems and cook for 4-5 minutes until bright green and just tender. Drain the broccoli, reserve a few small florets for garnish and transfer the rest to a blender. Add the vegetable broth and tofu. Place the lid on the blender and puree the broccoli mixture until smooth. Add the remaining teaspoon of truffle salt and the black pepper and blend again.
To serve, heat the soup over medium heat. Ladle into bowls and top with a scattering of broccoli florets and croutons. Serve.