Salsa de calçots (calçots' sauce) is a spanish sauce originating in valls, province of tarragona in the region of catalonia, which is served almost exclusively with calçots at the calçotades, a traditional local barbecue. it is similar to romesco sauce with the difference that it is thickened with toast rubbed with fresh garlic, moistened with a little vinegar and pulverized.
Source: Wikipedia