Boil noodles according to package instructions, then set aside.
Heat oil in a large pot over medium heat. Add Tom Yum Paste and mix until fragrant (about 1 minute).
Stir in the broth. Bring to a gentle boil.
Add mushrooms and simmer for 2-3 minutes until they are softened. Add shrimp and tomatoes and turn off the heat. The residual heat should cook the shrimp. Once they are pink, remove the pot from the burner.
Add fish sauce, lime juice, and brown sugar to taste.
Divide the cooked noodles among bowls. Ladle the hot Tom Yum broth over the noodles.
Top with slivered kaffir lime leaves, fresh cilantro, chili slices, and an extra squeeze of lime. Serve immediately.
