Prepare the Marinade: In a bowl, combine soy sauce, fish sauce, sesame oil, garlic, ginger, honey, and chili flakes. Whisk until well mixed.
Marinate the Beef: Add the sliced beef to the marinade, ensuring all pieces are coated. Cover and let it marinate for at least 20 minutes (or up to 2 hours in the fridge).
Cook the Beef: Heat a skillet or grill pan over medium-high heat. Cook the beef slices for 2-3 minutes per side, or until cooked through. Set aside to cool slightly.
Prepare the Vegetables and Wrappers:
Prep the Veggies: Julienne the carrots, cucumbers, and cabbage. Wash and pat dry the fresh herbs.
Soften the Rice Paper Wrappers: Fill a shallow dish with warm water. Dip one rice paper wrapper into the water for 5-10 seconds, until it softens and becomes pliable.
Assemble the Rolls:
Add Fillings: Lay the softened wrapper flat on a clean surface. Arrange a few slices of cooked beef, a handful of vegetables, and fresh herbs in the center. Add a slice of avocado if desired.
Roll Tightly: Fold the bottom edge of the wrapper over the filling, then fold in the sides. Roll tightly to seal. Repeat with the remaining wrappers and fillings.
Make the Dipping Sauce:
Mix the Sauce Ingredients: In a small bowl, whisk together peanut butter, soy sauce, lime juice, honey, and garlic. Gradually add warm water until the sauce reaches your desired consistency.
Serve:
Plate the Rolls: Arrange the rolls on a platter, seam-side down, and serve with the dipping sauce on the side.