Warm the olive oil in a wide pan. Add the garlic and cook, stirring frequently for about 90 seconds, then add the spices and salt, stir, and cook for 30 seconds more until toasted.
Add the collard greens, stirring well to coat with the spices, and continue to cook, stirring frequently, until softened and reduced in size by about half. Add the mirin/vinegar, stir in well, and quickly cover the pan with a lid. Reduce the heat to medium-low and let steam, covered, for about 5 minutes.
Remove the lid and stir well. If needed, continue cooking until desired softness is reached. Serve warm.