Bring a large pot of salted water to a boil.
Add the linguine and cook according to package directions until al dente. Just before draining, reserve about 1 cup (240 ml) of the starchy pasta water.
While the pasta cooks, prepare the chard.
Rinse it thoroughly and pat dry. Separate the leaves from the ribs.
Chop the ribs into 1-inch pieces and the leaves into 1-inch strips, keeping them in separate piles.
In a large skillet or Dutch oven, heat the olive oil and butter over medium heat.
Add the chopped garlic and red pepper flakes, and sauté for about 1-2 minutes until fragrant, being careful not to burn the garlic.
Increase the heat to medium-high.
Add the chopped chard ribs to the skillet and cook for 2-3 minutes, stirring frequently, until they begin to soften.
Add the chard leaves in batches, stirring until they wilt down.
Cook for another 3-5 minutes until all the leaves are tender but still bright green.
Season with salt.
Drain the cooked linguine and add it directly to the skillet with the Swiss chard.
Toss everything together to combine. If the pasta seems dry, add a splash of the reserved pasta water to create a light, silky sauce.
Serve immediately, topped with a generous amount of freshly grated Parmesan cheese.
Don't discard the chard stems! They add a wonderful texture and color to the dish.
Cooking them first ensures they become perfectly tender.
Add a can of drained cannellini beans or chickpeas along with the chard leaves for an extra boost of plant-based protein and fiber.
