Heat duck fat/olive oil in a small saucepan over medium heat.
Add garlic and cook, stirring occasionally, until soft (do not brown), about 5 minutes.
Add gochugaru and Sichuan pepper and cook, stirring occasionally, until fragrant, about 3 minutes; let cool.
Mix in scallion, cilantro, mint, lime juice, and vinegar; season with salt and pepper.