Heat the olive oil in a large, deep skillet or wok over high heat. Add sliced Brussels sprouts, give them a quick toss the in the oil, and then let them sit for a good minute to 2 minutes untouched so that they start to char in spots.
Stir and repeat until they're browned to your liking.
Reduce the heat slighlty. Add minced garlic and cook, stirring, for about a minute. {Careful not to scorch the garlic or it will become bitter.}
Meanwhile, in a small bowl, whisk together peanut butter, water, tamari {or soy sauce}, honey, lime juice and cayenne pepper until smooth.
Pour the sauce over the Brussels sprouts and toss to coat evenly. Cook for another minute or so.
Transfer to a serving dish and sprinkle with sesame seeds, if desired.