1teaspoonkosher or sea salt, more or less to taste
1/2teaspoonblack pepper, freshly ground, or more to taste
For the garnish:
1 1/2cupstortilla crisps or totopos, optional
1cupOaxaca cheese, or mozarella, diced, optional
In a soup pot set over medium-low heat, add butter and oil. Once the butter bubbles, stir in the onion, leeks and jalapeño. Cook, stirring sporadically, until the onion has softened, its color has become translucent, and the edges are beginning to brown lightly, about 12 to 15 minutes.
Raise the heat to medium, incorporate the zucchini and cook for about 3 to 4 minutes, stirring here and there. Pour in the broth, sprinkle with salt and pepper. Let it simmer for about 10 minutes, until the zucchini is thoroughly cooked and the soup has seasoned. Remove from the heat and let it cool slightly.
Place it all in the blender in batches and purée until smooth. Return the soup to the pot and let it thoroughly heat over medium heat. Serve very hot. Either spoon some diced cheese and totopos into each soup bowl right before eating, or let your guests add as much as they fancy.