Heat the olive oil in a large pot over medium heat. Add the chopped onions and sauté until soft and translucent. Add the garlic, zucchini, and kohlrabi and cook for a few minutes, stirring occasionally. Add the frozen broccoli, parsley, salt, pepper, and water.

Bring the mixture to a boil, then reduce the heat and simmer until all the vegetables are tender, about 40 minutes.

Blend the soup with an immersion blender until smooth or to your preferred consistency. Taste and adjust the seasoning with more salt or pepper if needed.

Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius).

Using a serrated knife, cut a small portion off the top of each hamburger bun. Carefully scoop out the center, leaving a solid base and sides without breaking through the bottom.

Place the bread bowls on a baking sheet lightly sprayed with oil and spray the each bowl with a little oil. Bake for 20 minutes or until crisp.

Serve the creamy broccoli soup in the freshly baked bread bowls and enjoy immediately.