To make the sauce, combine all the ingredients in a small bowl and whisk.
In a large pan, heat oil and then add garlic. Cook until light brown. Add eggs, noodles seasoning mix, serrano chillies and cook until eggs are lightly scrambled.
Add shrimp and onion and fold constantly until the shrimp turn pink, about 1 minute.
Add the noodles, basil, tomatoes and sauce and toss for about 3 minutes.
Cook for additional 1 minute until noodles are coated well in the mixture. Serve warm.