Butter a large cookie sheet and line it with wax paper. Set aside.
Melt half of the chocolate in a double boiler, set over a pan of hot water. When chocolate has melted completely, remove top part of double boiler. Add remaining chocolate and stir until melted and smooth.
Insert a candy thermometer into melted chocolate to check for ideal temperature - 88 to 90° F for bittersweet chocolate, 86 to 88° F for white or milk chocolate). If chocolate is too cold, place it back over the hot water. If too hot, let it cool until desired temperature is reached.
Add mix-ins all at once. Stir with a wooden spoon until they are thoroughly coated with chocolate.
Pour chocolate mixture onto prepared cookie sheet and spread with a spatula or wooden spoon to a thickness of one-half inch. (Don't worry if it doesn't reach the sides and corners of the cookie sheet, as the finished candy will be broken into free-form shapes.)
Let the bark set up and harden at room temperature, about four hours. (You can speed up the process by first placing the bark in the refrigerator for 10 minutes, but no longer.)
Grab the edges of the cooled bark and peel it off the wax paper in one piece, if possible. Break it with your hands into irregular pieces, about the size of a credit card. Store in an airtight container at room temperature for up to one month.
For nut bark: Add four oz. of lightly toasted whole almonds, macadamias, or pecan or walnut halves.
For apricot nut bark: Add one-half cup chopped dried apricots with the nuts.
For cherry or cranberry nut bark: Add one-fourth cup whole dried cherries or cranberries with the nuts.
For cinnamon nut bark: Add one tsp ground cinnamon with the nuts.
For raisin peanut bark: Add three-fourths cup raisins and one-fourth cup coarsely chopped salted peanuts.
For peppermint bark: Add one-half tsp mint extract and two-thirds cup of crumbled peppermint candies.Servings: