"But Madame, if you buy the large bag, you're paying much less per kilo," the shopkeeper explained. Sold. You don't want to know how much that "low, low" price was, although I'm sure it's less than buying it bar by bar. But this is 40% Valrhrona chocolate--the good stuff. And I know I'll work my way through it--eventually.
In summary: go find some milk chocolate (hint: it doesn't *have* to come from Hershey, Pennsylvania) and make these. You won't regret it.
1 c. (8 oz.) butter, room temperature
1/2 t. salt (Maida calls for 1/4 t., but I think a cookie like this calls for more of a hit of salt)
1 t. vanilla
1 c. (7 oz.) brown sugar
1 egg yolk
2 c. (8 oz.) sifted flour
About 8 oz. milk chocolate, in thin bar form: chips might work as well
1-1/4 c. (5 oz.) walnuts, chopped fairly fine
Heat the oven to 350; grease a 9x13-inch pan. Beat the butter, salt, and vanilla with an electric mixer until soft and fluffy. Add the brown sugar and beat for a minute or two. Beat in the egg yolk until mixed, then gradually beat in the flour at low speed. Make sure to scrape the bowl well in between beatings so that you don't have the pockets of pure sugar I seem to have in my cookies (see photo). Drop spoonfuls of dough all around the prepared pan, then cover with a sheet of waxed paper and use your fingers or the bottom of a measuring cup to pat the dough into a fairly even layer that covers the bottom of the pan. Remove the waxed paper. Bake the cookies 23 minutes, until the dough is evenly golden--it will puff up and then settle down. While the cookies are baking, unwrap the chocolate so that it is ready to go on top of the cookie layer as soon as it comes out of the oven. You can use the time to chop the walnuts as well.
As soon as the cookies come out of the oven, cover the cookie layer with a layer of chocolate. You may need to break up some of the bars to make them all fit. If the chocolate bars are thin enough, they should melt within a minute or so, and you can spread the chocolate evenly with the back of a spoon. If the chocolate doesn't want to melt, put the bars back in the oven for just a minute. Sprinkle the walnuts over the chocolate and press them lightly so that they stick to the chocolate. Let the bars cool to room temperature and then chill them for an hour or so for the chocolate to harden. Cut the cookies into at least 32 rectangles.