In a large pot, heat oil over medium heat. Add onion and sauté, stirring occasionally, until translucent, about five minutes. Add garlic and cook until fragrant.

Add peppers and continue to sauté until softened. Add eggplant and zucchini and cook, stirring occasionally, until they start to soften. Add tomatoes, herbs (if desired), salt, and pepper, and cook over medium heat until the mixture comes to a simmer.

Reduce heat to low, cover, and cook until the vegetables are tender, about 10 minutes. If the mixture is liquidy, uncover the pot and continue to cook over high heat until some of the moisture evaporates and the mixture thickens. Taste and adjust seasoning, adding a pinch of sugar, if desired.

To make stuffed mushrooms, preheat oven to 400 degrees Fahrenheit (200 degrees Celsius).

Remove the mushroom stems and place a tablespoon of ratatouille into each mushroom cap. Arrange the mushroom caps on a greased baking sheet.

Sprinkle with chopped almonds and drizzle with olive oil. Season with salt and pepper and roast until mushrooms are tender, about 25 minutes. Garnish with fresh basil.