Step 1Put TVP in a bowl. Pour over stock. Leave TVP to soak for 10 minutes until softened, then drain.
Step 2Heat oil in a frying pan. Add onion and gently fry for 5 minutes until soft. Add TVP. Fry for 4 more minutes, or until browned. Sprinkle chilli seasoning over and stir well.
Step 3Add chopped tomatoes and tomato paste. Simmer for 5-10 minutes until thickened. Season to taste, then remove from heat.
Step 4For avocado salad, place avocado, onion, tomatoes, lemon juice, tarragon and Tabasco in a bowl. Gently mix. Season to taste.
Step 5Heat tortillas. Fill with lettuce, TVP mixture, avocado salad and sour cream. Roll up and serve.