After a recent trip to France, I have become mildly obsessed with making macarons (using this recipe). I have made a couple of batches so far - the first didn't turn out well, more like cookies than macarons, due to under-whipped egg whites and too-coarse almonds.
The second batch has turned out better, much more like macarons. I whipped the egg whites to stiff, glossy peaks and blitzed the almonds, powdered sugar and cocoa in a food processor to remove lumps and make the almonds finer. Some of the macarons even have the characteristic little 'feet'.
However, while the flavour and texture seem generally good, they don't have the smooth, perfect surface of a proper macaron. Looking at videos online, it would seem my mixture is too stiff, because any little tip of mixture left by the piping bag fails to 'melt' into the main part of the macaron - it simply sits there. Also, any little craters left by air holes in the mixture fail to smooth themselves out, so the result is a bumpy macaron.
Given that the egg whites need to be stiff and glossy, what else could be a factor in achieving a smooth macaron? I assume the amount of powdered sugar is a factor, but how much can I safely reduce the amount by?