To temper chocolate, cover a heating pad with a kitchen towel, and set pad to lowest setting. Line two baking pans with parchment paper, and set aside. Using a sharp knife, shave chocolate.
In a medium glass bowl, heat two-thirds of the chocolate in microwave at 30 percent power for 1 minute. Stir chocolate, and continue heating at 30 percent power in 10-second intervals until an instant-read thermometer registers 120 degrees. Remove from microwave.
Stir in remaining shaved chocolate with rubber spatula. Stir constantly, bringing chocolate up sides and back down into bowl until temperature reaches between 86 degrees.and 89 degrees. To determine if tempered, drizzle a thin line onto a cool stainless-steel surface. The chocolate should dry to a matte finish in about 5 minutes. Place bowl on covered heating pad; stir occasionally to maintain temperature between 86 degrees.and 89 degrees. adjusting setting if necessary.
Working quickly, pour 2 tablespoons of tempered chocolate onto prepared sheets to form 2-inch patties, spaced 2 inches apart. Let chocolate stand until it just begins to set. Sprinkle 1 teaspoon chopped nuts in each center; set aside in cool place to harden. Once completely set, transfer to an airtight container at room temperature for up to 1 month.
Instead of melting the chocolate in the microwave, you can alternatively melt it over a water bath. To do so, fill a saucepan with 2 inches of water, and bring to a simmer; turn off heat. Set bowl with two-thirds chopped chocolate over pan, and stir gently with a rubber spatula until chocolate has melted and an instant-read thermometer registers 118 degrees. Remove bowl from pan. Add reserved chopped chocolate. Stir constantly, bringing chocolate up sides and back down into bowl, until temperature cools to about 86 degrees. Drizzle a thin line of chocolate on a stainless-steel surface to see that it is tempered, then return bowl to saucepan; stir occasionally to maintain temperature between 86 degrees and 89 degrees, returning to heat, if necessary.