Reduce the heat to medium.
In the same skillet, melt the butter.
Add the garlic and ginger. Sauté for about 1 minute, stirring often, until fragrant. Do not let the garlic burn.
Stir in the coconut milk, soy sauce, honey, optional fish sauce, lime zest, and 1 tablespoon fresh lime juice.
Bring the sauce to a gentle simmer, not a hard boil.
Simmer uncovered for 5–7 minutes, stirring occasionally, until the sauce thickens slightly and coats the back of a spoon.
Taste and adjust with more lime juice for brightness, more honey for sweetness, or more soy sauce or salt for savory depth.
If the sauce becomes too thick, add low-sodium chicken broth a splash at a time until it reaches your desired consistency.