1. Chop 1 pound of room temperature chocolate into 1/2-inch pieces.
2. Put 2/3 of the chocolate in a glass bowl. Microwave at medium-high power for 30-second periods, stirring with a rubber spatula in the intervals, until 3/4 of the chocolate is melted, about 1 1/2 minutes.
3. Stir the chocolate until completely melted, then scrape it into a clean, dry, room temperature bowl. Measure the temperature of the chocolate with an instant-read thermometer; it should be between 100 and 115 degrees. Add the remaining chocolate in large handfuls, stirring constantly until the chocolate is at 88 degrees. If the chocolate becomes too cool, melt a few more tablespoons of chopped chocolate and stir them in to raise the temperature.
4. Dip the tip of a knife in the chocolate; the chocolate on the knife should begin to set within 1 minute. Use at once.