This creamy pesto pasta has been my weeknight lifesaver for years. I first developed the combination of a classic white sauce with store-bought basil pesto one rainy evening when I had leftover pesto in the fridge and a box of pasta in the pantry. The result was unexpectedly luxurious: a glossy, herb-scented sauce that clings to every strand of pasta and comforts like a warm blanket. It became my short-notice company dish and the one my friends ask me to bring whenever we share a potluck.

What makes this preparation special is how few ingredients yield a rich, satisfying bowl. The butter and flour create a smooth roux that tames the milk into a silky binder for the pesto, while a little reserved pasta water can magically bring everything together. Texture is key: the sauce should coat rather than drown the noodles, and the bright green pesto keeps each bite lively. I often think back to the first time my partner closed their eyes after a forkful and declared it "restaurant good" — that memory keeps me making this over and over.

Ingredients

• Butter — 1/4 cup: Use unsalted if you want full control of seasoning. High-quality European-style butter adds a rounder mouthfeel; avoid margarine for best flavor and texture.
• All-purpose flour — 1/4 cup: This forms the roux that thickens the milk. For a gluten-free option, swap with a 1:1 gluten-free flour blend and whisk well to avoid lumps.
• Milk — 2 cups: Whole milk gives the creamiest result; 2% works fine but reduce thinning liquids slightly. For lactose-free or dairy-free versions, see substitutions below.
• Salt — 1/2 to 1 teaspoon: Start with less and taste; pesto and any added cheese will contribute additional saltiness. Use kosher or sea salt for cleaner seasoning.
• Pesto — 1/2 to 3/4 cup: Choose a bright basil pesto from a reputable brand, or use homemade basil pesto. Adjust amount to taste; fresher, oilier pesto yields a wetter sauce.
• Pasta — 3/4 pound (about 12 ounces): Use shapes that hold sauce well — fusilli, penne, farfalle or spaghetti all work. Dried semolina pasta has the best bite after draining.
• Optional — reserved pasta water or extra milk: A few tablespoons of starchy pasta water help emulsify and thin the sauce as needed.

Instructions

Bring the water to a rolling boil and cook pasta: Fill a large pot with at least 4 quarts of water and add a generous pinch of salt. Bring to a rolling boil, then add the pasta and cook according to the package for al dente. Reserve 1/2 to 1 cup of pasta water just before draining — the starch in this water is a key emulsifier for the sauce. Make the white sauce (roux-based): While the pasta cooks, melt 1/4 cup butter in a medium saucepan over medium heat. When the butter is foaming, sprinkle in 1/4 cup flour and whisk continuously for 2 minutes to cook the raw flour taste away. The mixture should smell slightly nutty and turn pale blond. Whisk in the milk and thicken: Slowly pour 2 cups milk into the roux in a thin stream, whisking constantly to prevent lumps. Increase heat to medium-high and continue whisking until the sauce thickens and coats the back of a spoon, about 4 to 6 minutes. If it becomes too thick, whisk in 1 to 2 tablespoons reserved pasta water or a splash more milk to reach a saucy consistency; remember it will loosen more once pesto is added. Season and blend with pesto: Remove the pan from heat and stir in 1/2 to 3/4 cup pesto until evenly combined. Taste and add 1/2 to 1 teaspoon salt as needed, keeping in mind pesto can be salty. The sauce should be glossy and pourable. Toss pasta with the sauce and finish: Drain the pasta and return it to the warm pot. Pour the pesto cream sauce over the noodles and toss gently until every piece is coated. If the sauce seems heavy, add 1 to 2 tablespoons reserved pasta water and toss again to emulsify. Add cooked protein or greens at this stage, then serve immediately with an optional grating of Parmesan.

Storage Tips

Store leftovers in airtight containers in the refrigerator for up to 3 days. To avoid the sauce tightening, pack a small container of extra milk or keep a few tablespoons of reserved pasta water in the fridge with the pasta; add when reheating. Reheat gently on the stovetop over low heat, stirring frequently and adding a splash of liquid to restore creaminess. Avoid reheating at high heat to prevent curdling. Do not freeze the fully finished pasta — freeze only the pesto or cooked plain pasta separately if you want longer storage.

Ingredient Substitutions

For a gluten-free version, use a certified gluten-free flour blend for the roux and gluten-free pasta. To make it dairy-free, substitute the butter with vegan butter and use an unsweetened, neutral plant milk such as oat or soy; be aware the sauce might have a slightly thinner mouthfeel. Swap jarred basil pesto for sun-dried tomato pesto or a kale walnut pesto to vary flavor; if your pesto contains nuts and you need a nut-free option, choose a seed-based pesto or make a simple basil-oil emulsion instead.

Serving Suggestions

Serve with a crisp green salad dressed with lemon and olive oil to cut through richness. Roasted cherry tomatoes or blistered peppers add sweetness and texture contrast. Offer grated Parmesan or Pecorino cheese at the table for guests who want extra umami. For a casual meal, crusty bread is perfect for mopping up any leftover sauce. Present in shallow bowls and sprinkle a few torn basil leaves and a drizzle of good olive oil for restaurant-style plating.

Cultural Background

This preparation blends classic French technique — a roux-thickened white sauce — with Italian pesto, a Ligurian green sauce traditionally made from basil, pine nuts, garlic, Parmesan and olive oil. Combining these methods creates an Italian-American hybrid that gives pesto a creamier vehicle while preserving its herbaceous brightness. The approach reflects how home cooks adapt regional sauces to suit pantry availability and preference for texture, making the dish accessible yet rooted in Mediterranean flavors.

Seasonal Adaptations

In spring and summer, use fresh basil pesto (homemade or from a farmer’s market) for the brightest flavor and pair with peas or asparagus. In autumn and winter, swap basil pesto for a roasted squash or sage walnut pesto for a deeper, earthy profile. For holiday gatherings, finish with toasted pine nuts and a squeeze of lemon to brighten the plate. The basic method adapts easily to seasonal produce while keeping the same comforting creaminess.

Meal Prep Tips

Prepare the sauce up to 2 days ahead and store it chilled; reheat gently and toss with freshly cooked pasta to prevent the sauce from breaking. Cook pasta in bulk and keep it al dente; refresh briefly in boiling water before combining with sauce to restore texture. Portion into single-serving containers with a small container of reserved pasta water for quick lunches. Label and date containers, and consume within 3 days for best quality.

Every time I make this I discover a small tweak — a squeeze of lemon, a handful of baby arugula, or a different pesto — that makes it feel new. That flexibility keeps it in my regular rotation, and I hope it becomes one of your reliable, delicious go-to meals too.