sweet stones of Perosa I saw pictures of some sweet buns that look striking, and I cannot find a recipe. The buns are described as "sweet stones of Perosa."
Here is a picture of sweet stones of Perosa, and another of sweet stones of Perosa in a basket.
How does one achieve the stone look? 
The pictures are from a web site that promotes the town of Perosa Argentia, the implication being that these are traditional bake goods from that region of Piedmont, as such, I assumed the silver coating is achieved by means accessible to a country cook. I thought may be eatable charcoal mixed with something could produce the effect, but I have no idea.
There's a couple of options. I've never heard of "sweet stones of Perosa", but if the recipe actually goes back many years then it's likely it originally used extremely thin silver (or other metal) foil, stuck to the buns and then baked.

Those pictures don't look like edible foil, though. The silver is attenuated at the sides. That makes me think they're using spray-on silver food coloring (basically edible spray paint).

In either case, the coloring is likely applied before baking, and as the buns puff up the colored area cracks, making the buns look rocky rather than just silver.