The recipe calls for high power, but if you've got a newer, more powerful microwave, we suggest using a more conservative approach, especially if this is your first foray into tempering chocolate with your microwave. Start on medium power (100-110°F), and stop and stir your chocolate every 20-30 seconds until it's smooth and shiny. If it appears grainy or unusually dry and chunky, it's likely been burned and should be tossed. Trust us, we know firsthand the disappointment of having to chuck a bunch of chocolate. Better safe than sorry. Lower heat.