These bars freeze well, so it's nice to make extras to keep in the freezer for anytime you want a quick treat. Before cutting the bars, if you dip your knife into hot water to heat it, it will help make the process neater and cut easily through the chocolate.

After this recipe was first published, I got the following email from reader Sandra Merz, who lives in Vancouver, about a delicious variation:

In a heavy saucepan melt 1/2 cup butter 2 ounces of the chocolate. Remove from the heat and stir in the sugar, egg, oats, chopped nuts, coconut and 1 teaspoon of vanilla extract. Press mixture into prepared pan and chill for 1 hour.

Mix the confectioner's sugar with the softened butter, 1/2 teaspoon vanilla and the milk. Beat until the icing is smooth. Spread it over the oat mixture and chill for 1/2 hour.

Melt the remaining 1 tablespoon butter with the remaining 2 ounces of chocolate. Spread over the top of the bars and chill for at least 4 hours before cutting into bars.