Heat a large heavy-bottomed pot over medium heat. Add olive oil and butter. When butter foams, add diced onion, carrot, and celery. Cook, stirring occasionally, until softened and translucent, about 7–8 minutes.

Garlic and roux

Add minced garlic and cook 30 seconds until fragrant. Sprinkle the flour over the vegetables and stir continuously for 1–2 minutes to cook the raw flour taste and form a light roux.

Deglaze and add stock

If using, pour in the white wine to deglaze the pan, scraping any browned bits from the bottom; simmer until mostly evaporated, about 2 minutes. Add the stock, bay leaf, thyme sprigs, salt, and black pepper. Bring to a gentle simmer.

Main Vegetables & Protein

Cook root vegetables

Add the diced potato to the simmering broth. Simmer gently until the potato is nearly tender, about 12–15 minutes.

Add remaining vegetables and beans

Add the diced zucchini and cannellini beans to the pot. Continue simmering until zucchini is tender and flavors meld, about 6–8 minutes.

Add greens

Stir in the chopped spinach and cook just until wilted, about 1–2 minutes. Taste the broth and adjust seasoning with additional salt and pepper if needed.

Finishing & Garnish

Brighten and finish

Remove and discard the bay leaf and thyme stems. Stir in the lemon juice, grated Parmigiano-Reggiano, and red pepper flakes. Off heat, swirl in the finishing extra-virgin olive oil.

Serve

Ladle the soup into bowls, sprinkle with chopped parsley and an extra pinch of cheese or red pepper flakes if desired. Serve hot with crusty bread.