Heat large covered saucepan of salted water to boiling over high heat. Add spaghetti and cook as label directs; drain pasta, then return to saucepan.
Meanwhile, heat large skillet over medium-high heat. Add bacon and cook 10 minutes or until crisp, stirring frequently. Add garlic and cook 1 minute, stirring. Remove skillet from heat; carefully drain off fat. Add cream to bacon and cook over medium-high
In small bowl, lightly whisk eggs with chives, if using. Slowly stir eggs into skillet. Pour sauce over spaghetti. With tongs, toss spaghetti with sauce until well combined. Sprinkle with cheese to serve.