Heat oven to 350 degrees. Remove any discolored outer leaves and trim stem portion of brussels sprouts. In a 3-quart saucepan, place brussels sprouts; add enough water just to cover. Heat to boiling; boil 6-8 minutes or until crisp-tender. Drain and return to saucepan; set aside.
Meanwhile, in a 10-inch skillet, cook bacon over medium heat, stirring occassionally, until crisp. Remove bacon and drain on paper towels; set aside. Drain all but 1 tablespoon bacon fat from skillet.
Add butter to bacon fat in skillet. Heat over medium-high heat until butter is melted. Add onion; cook 2-3 minutes, stirring frequently, until crisp-tender. Add flour, thyme and pepper; cook and stir until well-blended. Gradually stir in half-and-half and bouillon granules. Heat to boiling, stirring constantly; boil and stir 1 minute. Remove from heat and stir in Parmesan cheese.
Pour sauce over brussels sprouts in saucepan; mix gently. Spoon into 2-quart casserole. Bake uncovered 25-30 minutes, sprinkling with crumbled bacon and Cheddar cheese for last 10 minutes of baking, until hot and bubbly. Serve right away.