The management of spontaneous light emission at the nanoscale is a crucial aspect in many application domains dealing with lighting, optical communications and quantum information systems. Two widespread approaches to target this topic are based on plasmonic structures and dielectric photonic crystals, which have demonstrated a high potential in controlling spectral, angular and temporal features of the emission. Both approaches exhibit rather complementary advantages, and many efforts are nowadays undertaken to find hybrid solutions taking the best from the two sides. In this framework, we propose a photonic device based on a dielectric multilayer, which is shown to control the spontaneous emission from organic dyes embedded therein. Such a result is achieved by exploiting the near-field interaction of emitters to Bloch Surface Waves resonantly coupled within a subwavelength cavity surrounded by a diffractive structure. A bright, monochromatic spontaneous emission is then obtained, with spectral width below 1 nm, an average decay rate increased by more than 1 order of magnitude, and a propagation divergence below 5° in free space. These findings are particularly promising for application in integrated photonic circuits and single-photon sources.