Brown ground beef in a large skillet over medium-high heat, breaking up frequently with a spoon or spatula to achieve a fine cooked ground beef texture (i.e., small pieces), 8-10 minutes.

Add broth to beef. If broth is unseasoned, add 1/2 teaspoon of salt.

Let simmer, stirring occasionally, until broth has completely boiled away, about 6-8 minutes.

Meanwhile, combine crushed garlic, lime juice and fish sauce.

Finely chop and then combine cilantro and mint in a separate bowl.

Separate lettuce leaves and cut in half if very large.

Once broth has boiled off completely (if you listen carefully, you can hear the moment that there’s no longer any water in the pan), stir in the lime juice mixture.

Simmer, stirring, until the lime juice mixture has also boiled away, about 2-3 minutes.

Stir in chopped herbs, immediately remove beef from heat and serve on lettuce leaves.