Brown the beef: Heat a large skillet over medium-high heat. Add the ground beef and cook until fully browned, about 6-8 minutes. Drain the excess fat.

Season the beef: Stir in the taco seasoning along with a splash of water. Allow it to simmer for 3-4 minutes.

Make the roux: In a separate saucepan, melt the butter over medium heat. Whisk in the flour to create a roux, cooking it for about 1 minute until bubbly.

Whisk in cream: Gradually add the milk or heavy cream, whisking continuously until smooth, about 3-5 minutes.

Melt the cheeses: Add in the cheddar and Monterey Jack cheeses, stirring until melted. Mix in the cream cheese.

Adjust consistency: Whisk in more milk if needed for desired thickness.

Warm the shells: Preheat your oven or a skillet to warm taco shells for about 5 minutes.

Assemble the tacos: Fill each taco shell with seasoned beef and drizzle with cheese sauce.

Add toppings: Top with diced tomatoes, onions, and cilantro or lettuce.

Serve immediately: Enjoy hot with lime wedges or hot sauce.