Place a large skillet over medium-high heat and brown the ground beef until fully cooked, approximately 6-8 minutes. Drain excess grease.
Add the diced onion to the skillet and sauté for 3 minutes until softened.
Stir in the minced garlic and tomato paste, cooking for 1 minute until fragrant.
Add the dry orzo pasta to the skillet, stirring for 1 minute to lightly toast the grains.
Pour in the beef broth, mustard, salt, and pepper. Bring the mixture to a boil.
Reduce heat to low, cover the skillet, and simmer for 10-12 minutes or until the orzo is al dente and most liquid is absorbed.
Remove from heat and fold in the shredded cheddar cheese until completely melted and emulsified.
Top with diced dill pickles and serve immediately.