Bring a large pot of salted water to a boil and add the penne pasta. Cook according to the package instructions for about 8-10 minutes, until al dente. Two minutes before the pasta is done, add the fresh broccoli florets to the pot. Once cooked, drain the pasta and broccoli in a colander and set aside.

In a large skillet over medium heat, melt 2 tablespoons of unsalted butter. Once the butter is bubbly, add the sliced kielbasa sausage, cooking for about 5 minutes until the edges are golden brown and crispy.

Stir in the diced yellow onion and minced garlic into the skillet with the kielbasa. Sauté for an additional 2-3 minutes until the onion becomes translucent.

In a small bowl, whisk together 2 tablespoons of cornstarch with 1 cup of whole milk until smooth. Pour this mixture into the skillet, stirring continuously until the sauce thickens.

Reduce the heat to low and gradually stir in 1 cup of shredded mild cheddar cheese until fully melted and creamy.

Add the drained penne pasta and broccoli into the skillet, tossing gently to combine everything. Season with salt and pepper, serve warm.