Italian Penicillin Soup Recipe
A comforting, science-backed Italian Penicillin Soup (Pastina) made with rich chicken broth, tiny pasta, egg, and Parmigiano-Reggiano.
- Starch gelatinization from cooking pastina directly in broth creates a naturally thick, velvety body without heavy cream.
- Tempering the egg-cheese mixture prevents curdling, ensuring a silky, cohesive emulsion.
- Finely minced mirepoix provides a sweet, aromatic base that balances the savory depth of the chicken stock.
The secret to a flawless Italian Penicillin Soup lies in starch gelatinization and precise egg tempering. Cooking the tiny pastina directly in broth allows surface starches to naturally thicken the liquid.
Tempering the egg prevents protein coagulation from turning lumpy.
To execute this technique, whisk a fresh egg with finely grated Parmigiano-Reggiano before slowly introducing hot broth to raise its temperature gradually. This step stabilizes the egg proteins, allowing them to emulsify smoothly into the soup. The result is a rich, cohesive emulsion that coats the palate.
While a traditional Chicken Noodle Soup relies on clear broth, this Italian classic aims for a creamy, bound texture.
This emulsification method is chemically similar to the technique used in Egg Drop Soup, where hot liquid cooks the egg gently. The addition of cheese here adds fat, which further stabilizes the mixture.
Italian Penicillin Soup
Ingredients
- 4 cups high-quality chicken broth (preferably homemade or bone broth)
- 1/2 cup pastina pasta (such as stelline or acini di pepe)
- 1 small carrot, peeled and extremely finely minced
- 1 small celery stalk, extremely finely minced
- 1/2 small yellow onion, extremely finely minced
- 1 large egg, room temperature
- 1/4 cup Parmigiano-Reggiano cheese, finely grated (plus more for serving)
- 1 tablespoon unsalted butter
- Kosher salt and freshly cracked black pepper to taste
Directions
- In a medium saucepan, combine the chicken broth, finely minced carrot, celery, and onion. Bring to a boil over medium-high heat, then reduce to a simmer, cover, and cook for 10 minutes until the vegetables are tender.
- Stir the pastina into the simmering broth. Cook uncovered for 6 to 8 minutes, stirring frequently to prevent the tiny pasta from sticking to the bottom of the pan, until the pasta is al dente.
- While the pasta cooks, whisk the egg and finely grated Parmigiano-Reggiano together in a small heatproof bowl until a smooth paste forms.
- Remove the saucepan from the heat source. Slowly ladle about 1/4 cup of the hot broth into the egg and cheese mixture while whisking constantly to temper the egg and prevent curdling.
- Pour the tempered egg mixture back into the saucepan, stirring vigorously to incorporate it into the soup. Add the unsalted butter and stir until melted and fully emulsified. Season with kosher salt and freshly cracked black pepper to taste, and serve immediately. </
Notes
Always use freshly grated cheese to ensure proper melting and prevent clumping.
- Brand-specific recommendation: Use Diamond Crystal Kosher Salt; if substituting Morton Kosher Salt, reduce the volume by half to avoid over-salting the delicate broth.
- Science-backed rationale: The egg must be tempered off the heat because direct exposure to temperatures above 144°F (62°C) causes egg proteins to denature and clump, ruining the smooth emulsion.
- Preemptive workflow warning: If you skip stirring the pastina during the first two minutes of boiling, the starch-heavy pasta will settle and fuse to the bottom of the pan. Prevent this by maintaining a gentle boil and stirring continuously.
- Storage behaviour note: After 24 hours in the refrigerator, the pastina will continue to absorb liquid, swelling significantly and turning the soup into a thick porridge-like consistency.
- Equipment alternative: If a traditional saucepan is unavailable, a heavy-bottomed Dutch oven works excellently as a backup, though you may need to reduce the cook time by 2 minutes due to its high thermal mass.
Serving Suggestions
Complete this comforting bowl by pairing it with elements that offer contrasting textures and bright acidity to cut through the rich, egg-bound broth.
- Serve alongside warm, crusty Artichoke Bread to provide a crunchy, garlic-infused contrast to the soft pastina.
- A simple arugula salad dressed with fresh lemon juice and olive oil cuts through the soup's rich, savory fat.
- Top each bowl with an extra grating of aged Parmigiano-Reggiano and a drizzle of high-quality extra virgin olive oil for a punch of raw, peppery flavor.
- Pair with a side of roasted vegetables to add a caramelized, earthy element to the meal.
Storage and Reheating
Store any leftover soup in an airtight glass container in the coldest zone of your refrigerator for up to 3 days.
Do not freeze this soup; the starch structure of the pastina will break down upon thawing, resulting in a mushy, unappealing texture.
To reheat, place the soup in a small saucepan over low heat, add 2 to 3 tablespoons of fresh chicken broth or water to restore the liquid balance, and stir constantly until warmed through.
Avoid reheating in the microwave if possible, as uneven heating can cause the egg emulsion to break and separate.
Ingredient Substitutes
You can adapt this recipe to suit dietary needs or pantry availability with minor technical adjustments.
- Original: Pastina pasta. Substitute: Orzo or acini di pepe. Ratio: 1:1. Adjustment: Increase the pasta boiling time by 2 to 3 minutes as these larger shapes take longer to hydrate.
- Original: Chicken broth. Substitute: Rich vegetable broth. Ratio: 1:1. Adjustment: Add a teaspoon of soy sauce or nutritional yeast to the vegetable broth to replicate the savory glutamates of chicken stock.
- Original: Parmigiano-Reggiano. Substitute: Pecorino Romano. Ratio: 1:1. Adjustment: Pecorino is significantly saltier than Parmigiano; reduce the added kosher salt in the final step to compensate.
Master this simple tempering technique, and you will have a comforting, restorative meal ready in under thirty minutes. Keep your heat low during the final emulsion step to ensure a silky finish every time. Enjoy the precise balance of rich broth, tender pasta, and savory cheese.