In a large heavy-bottomed pot or Dutch oven, heat butter and olive oil over medium heat until butter melts and foams. Add diced onion, carrot, and celery. Cook, stirring occasionally, until vegetables are softened and the onion is translucent, about 6–8 minutes. Add minced garlic and cook until fragrant, about 30–45 seconds; do not let it brown.

Vegetables & Add-ins

Add hearty vegetables

Add diced potato and sliced mushrooms to the pot. Cook, stirring occasionally, 4–5 minutes until mushrooms begin to release moisture and soften.

Add remaining vegetables

Stir in diced zucchini and frozen peas. If using the canned diced tomatoes, add them now with their juices. Cook for 2 minutes to combine flavors.

Liquids & Seasoning

Deglaze and simmer

If using, pour in the white wine and scrape up any browned bits from the bottom of the pot; let the wine reduce by half, about 1–2 minutes. Add the chicken or vegetable stock and 1 cup water. Stir in the bay leaf, dried thyme, dried oregano, salt, and pepper. Bring the mixture to a gentle boil over medium-high heat.

Simmer until tender

Reduce heat to low and simmer, partially covered, until the potatoes and other vegetables are tender, about 15–20 minutes. Check and stir occasionally.

Finish & Garnish

Adjust seasoning & finish

Remove the bay leaf. Taste the soup and adjust seasoning with additional salt and pepper if needed. Stir in the chopped parsley, lemon juice, and grated Parmesan (if using). For a creamier texture, use an immersion blender to purée 1–2 cups of the soup in the pot, then stir to incorporate; alternatively, ladle 1–2 cups into a blender, purée until smooth, and return to the pot.

Serve hot in bowls, garnished with an extra sprinkle of parsley and grated Parmesan if desired.