Boil water in a large pot. Add penne pasta and cook until al dente, about 8-10 minutes. During the last 2 minutes, add broccoli florets. Drain and set aside.

In a large skillet, melt butter over medium heat. Add sliced kielbasa and cook for 5 minutes until browned.

Stir in diced onion and minced garlic. Cook for 2-3 minutes until onion is translucent.

In a bowl, whisk cornstarch with whole milk. Pour into skillet and heat until simmering, stirring for 3-5 minutes until thickened.

Reduce heat and stir in shredded cheddar cheese until melted and smooth.

Add drained pasta and broccoli to skillet, tossing until well-coated in sauce. Season with salt and pepper.

Remove from heat and garnish with chopped parsley before serving.