In a medium saucepan, heat 1 tablespoon of olive or vegetable oil over medium heat. Sauté any desired aromatics like chopped onion, minced garlic, or ginger for about a minute until fragrant.
Add the Thai red curry paste to the pan and stir constantly for 1-2 minutes.
Gradually whisk in the coconut milk and the broth (or water). Bring the mixture to a simmer over medium heat.
Stir in the fish sauce, sugar, and lime juice. Taste the sauce and adjust the amounts as needed.
Let the sauce simmer uncovered for about 10-15 minutes, or until it has reduced and thickened slightly.
Add your choice of cooked protein and vegetables, and simmer until they are cooked through and tender.
Stir in fresh Thai basil leaves or cilantro just before serving.
