Break or chop chocolate into pieces, if necessary, and melt either in microwave or in a double boiler over low heat. Stir in almonds. Pour out on a lightly buttered cookie sheet (preferably one with a slight rim) and spread out to desired thickness with a rubber spatula. Let cool to solidify, then break up in chunks.
The "bark" you find in the stores - here in the US, anyway - is usually Almond Bark, made with melted white chocolate and slivered, blanched almonds. I've never found the regular chocolate version, but it's presumably made the same way. I do know that in my local stores, you can buy packages of white chocolate in about 1" cubes to make it with. Don't remember the brand name, but it's usually sold in the baking section.
I don't know the exact measurements, either, as I just use one package to make a batch. However, it's pretty flexible anyway, as I always add more nuts than the recipe calls for. (I like lots of almonds!) As long as you have enough chocolate to bind the nuts together, it'll work. And of course, you can substitute pretty much any other kind of nut you like instead of almonds. May have to do your own blanching and slivering, though.
Voila. ;) Don't you just love really simple recipes? Just watch out for it disappearing fast...