Question: What blessing should be recited over homemade croutons made by cutting bread into small pieces and baking them in the oven, which are then placed into soup?

Answer: Since these croutons are made from bread and were baked in the oven rather than deep-fried in oil, their blessing remains Hamotzi, even though they are small pieces. However, if they are placed directly into a boiling pot their blessing changes to Mezonot, provided that each piece is smaller than a kezayit.
If they are placed only into a bowl of soup, their blessing remains Hamotzi. However, if they dissolve completely in the soup, then their blessing becomes Mezonot.