Add the chicken broth, coconut milk, lemongrass, kaffir lime leaves, and ginger to your slow cooker.

Add the sliced mushrooms and chicken pieces to the slow cooker and stir gently to combine.

Cover and cook on low for 4-5 hours, or until the chicken is fully cooked and tender.

Once cooked, remove the lemongrass stalks and ginger slices using a slotted spoon.

Stir in the fish sauce, lime juice, brown sugar, and chili paste (if using). Taste and adjust seasoning as needed.

Add the cherry tomatoes and cilantro to the soup, stirring gently to combine. Let it heat for 5-10 minutes.

Ladle the soup into bowls and garnish with sliced red chili and additional cilantro, if desired.