With embedded systems and IoT devices being widely deployed nowadays, their security becomes a major concern. Among all possible attacks, side channel attacks (SCA) represent a major source of threats. For power side channels, template attacks have been proven to be efficient and widely applicable. Traditional template attacks require physical access to an identical target device for extensive profiling to construct the attack template. In this paper, we present a composable template attack that relaxes this requirement by constructing the attack template as a composition of templates from individual architectural components, including processor, caches, and memories. The proposed approach enables an attacker to construct a template using only information of a system's components and device models thereof.