Peel, chop, and sauté the onion in a pot with olive oil.

Peel and chop the zucchini, then add them to the onions.

Cover with water, crumble in the bouillon cubes, and season with salt and pepper. Cook over medium-high heat until the vegetables are tender.

Blend the soup, then add the mascarpone (taste and adjust the amount as needed). Season again if necessary and blend until smooth.