In medium fry pan fry 4 slices of bacon till crisp; remove and place on paper towels. In the same pan add onion & garlic to the bacon grease with salt & pepper.Cook till tender. Add in flour and dissolve, slowly; pour in milk, stirring occasionally till it thickens. Add in tortellini, and bring to a boil over medium heat. Reduce to low and simmer and thickened., about 4 minutes. Remove from heat, add in bacon and cover with cheese. Transfer to baking dish, and broil till golden brown, about 3 minutes.