Place the chocolate in a 4-quart glass bowl. Microwave on high for 30 seconds, and then stir with a clean spatula. Repeat 2 more times. Microwave on high for 15 seconds, and then stir. Repeat 2 to 4 more times or until the chocolate reaches 100ºF. Microwave on high for 10 seconds, and then stir. Repeat 5 more times or until the chocolate reaches 115ºF.
Remove from the microwave and cool, stirring occasionally, until the chocolate reaches 95ºF. Add the cocoa butter and stir continuously until the cocoa butter melts and the chocolate cools to 90ºF.
Test the temper of the chocolate by spreading a small amount in an even layer on a metal surface set over an ice pack. It should set within 3 minutes and be shiny and streak free.
Maintain 90ºF by briefly heating the chocolate with a 10-second blast of warm heat from a hair dryer. Use immediately for dipping fruit, pretzels, cookies, etc.