Start by bringing a large pot of salted water to a boil. The salt will enhance the flavor of the pasta as it cooks. Once the water is boiling, add the pasta shells, stirring occasionally to prevent sticking. Cook the shells until they’re al dente—tender but still slightly firm when bitten. This typically takes about 8-10 minutes. Before draining, reserve one cup of the pasta water, which you’ll use later to adjust the sauce consistency. Drain the pasta and set it aside.
While the pasta cooks, heat two tablespoons of olive oil in a large skillet over medium heat. Add the diced onion, and cook, stirring frequently, until it becomes soft and translucent. This usually takes about 3-4 minutes. Then, add the minced garlic, cooking for another minute or so, just until it becomes fragrant and starts to turn golden. Be careful not to burn the garlic, as it can become bitter.
Next, add the broccoli florets and bell pepper slices to the skillet. Sauté the vegetables for about 5-7 minutes, stirring occasionally, until they become tender and lightly caramelized. If using quick-cooking vegetables like spinach or tomatoes, add them later in the cooking process, as they don’t need as much time to cook.
Reduce the heat to low and pour in the heavy cream, stirring gently to combine it with the vegetables and aromatics. Let the mixture simmer for a few minutes until it starts to thicken slightly. This step is crucial for a creamy texture, so allow the cream to heat gently without boiling.
Gradually add the grated Parmesan cheese to the skillet, stirring continuously to help it melt smoothly into the sauce. The cheese will thicken the sauce further and add a savory, umami flavor that complements the creamy base.
Add the cooked pasta shells to the skillet, stirring them gently to coat them evenly with the sauce. If the sauce seems too thick, gradually add the reserved pasta water, a few tablespoons at a time, until the sauce reaches your desired consistency. This starchy water will help the sauce cling to the shells, creating a more cohesive dish.
Taste the pasta and adjust the seasoning with salt and pepper to your preference. For a hint of heat, sprinkle a few red pepper flakes, if desired. Just before serving, garnish with freshly chopped basil or parsley to add a pop of color and a fresh, herbal aroma.
Transfer the creamy shell pasta to serving bowls, and add a final sprinkle of Parmesan if you like. Serve warm, and enjoy the rich, flavorful dish immediately!