Tortellini with Basil and Sausage

1 pound (1 bag) frozen cheese tortellini 1/2 pint grape tomatoes1 teaspoon olive oil1 large onion (for about 1 cup chopped) 1/2 pound breakfast-style hot sausage (see note)1 teaspoon bottled minced garlic 1/2 cup whole milk or half-and-half 1/2 cup firmly packed prewashed basil leavesBring 4 quarts of unsalted water to a boil. Add the tortellini, bring the pot back to a boil and cook according to the package directions until just tender, about 5 minutes. Drain well.Meanwhile, slice the tomatoes in half (or, if they are large, quarter them) and set aside.Heat the oil in a 12-inch extra-deep skillet over medium heat. Peel and coarsely chop the onion, adding it to the pan as you chop. Crumble the sausage while adding it to the pan with the onion. Cook, stirring frequently, until the sausage is browned and the onion begins to caramelize, about 5 minutes.Add the garlic to the cooked sausage. Add the sliced tomatoes and milk and stir well. Cut the basil leaves into thin strips (see note) and add to the sausage mixture. Reduce the heat to simmer until the tortellini is done. Then toss the drained tortellini with the sausage mixture and serve immediately.Serves four.Cook's notes: Most breakfast-style sausage brands come in 1-pound packages. Seal the remaining sausage in a zipper-top bag and refrigerate for another use. Stack the basil leaves on top of each other and then roll into a "cigar-shaped" roll. Slice perpendicularly, about 1/8-inch slices, and the leaves will unroll into thin strips, perfect for adding to the sausage mixture.Nutrition values per serving: 386 calories, 16 g fat (6 g saturated), 43 g carbohydrates, 5 g fiber, 17 g protein, 41 mg cholesterol, 532 mg sodium.