Line a cookie sheet with aluminum foil. In a double boiler melt the chocolate with the butter and oil over hot (not simmering) water. Stir constantly until the chocolate is melted and smooth.
Remove pan from double boiler and stir in the nuts to the melted chocolate. Pour the chocolate mixture onto the prepared cookie sheet. Spread randomly to the desired thickness. Refrigerate 20-30 minutes, or until set.
Slide a metal spatula under the chcolate to loosen it from the foil. Break into uneven pieces. Store in an airtight container or in the refrigerator.