Step 1: Heat olive oil in a large pot or Dutch oven over medium-high heat.
Step 2: Add ground beef and cook until browned, breaking it up with a spoon, about 5-7 minutes.
Step 3: Add diced onion and minced garlic to the pot, cooking until softened, about 3-4 minutes.
Step 4: Stir in penne pasta, beef broth, heavy cream, oregano, salt, and pepper. Bring to a boil.
Step 5: Reduce heat to medium-low, cover, and simmer for 12-15 minutes, stirring occasionally, until pasta is tender.
Step 6: Remove from heat and stir in cheddar and mozzarella cheeses until melted and creamy.
Step 7: Let sit for 5 minutes to thicken, then garnish with fresh parsley if desired before serving.