How to Make It
Trim and discard root end and tough outer leaves of lemongrass stalk; smash with flat side of knife.
Bring broth, garlic, ginger, and lemongrass to a boil in a covered Dutch oven over high heat. Reduce heat to medium; simmer 20 minutes. Remove from heat; let stand to infuse 15 minutes. Discard lemongrass and garlic.
Bring broth mixture to a boil over medium-high heat; stir in turkey, next 2 ingredients, and, if desired, jalapeño. Boil 3 minutes. Serve with toppings.
Speedy Lemongrass-Turkey Soup: Omit lemongrass, garlic, and ginger; substitute 1 (32-oz.) container Thai ginger-infused broth for reduced-sodium chicken broth. Omit Steps 1 and 2; prepare recipe as directed in Step 3.