In a large skillet over medium-heat, melt butter; add garlic and cook for 1 minute, stirring constantly. Add flour and sugar; cook for 1 minute, again stirring constantly. Slowly add the milk, whisking until mixture is smooth. Add the shredded cheese; stir until melted and smooth; season to taste with black pepper. Stir in frozen peas; reduce heat to medium and cook for 5 minutes, or just until peas are heated through. Enjoy!