In a large nonstick skillet, heat oil over medium. Add onion and cook 2 minutes. Add next 7 ingredients and 1/2 tsp salt. Cook, stirring to break up lamb, about 6 minutes, until browned.
Spread each warm tortilla with 1 Tbsp mint cream. Toss romaine with cilantro, mint, lemon juice and 1/8 tsp salt
Using a slotted spoon, divide lamb evenly amount tortillas and top with romaine mixture
Mint Creama:
Stir 1/2 cup sour cream, 1 tbsp each finely chopped mint and cilantro, 1 tbsp lemon juice, 1 tsp lemon zest and 1/8 tsp salt.