That's exactly what the README suggests to do under 'Usage'. First it says 'FROM node', which is the regular 'fat' image. In this image it then runs `npm install`. Further on there is another 'FROM' which starts from the minimal image and copies over all the JS code (including the node_modules directory which has been populated by npm) from the 'fat' image (this of course would fail for bindings that require libraries outside the node_modules directory, although it is relatively easy to add more COPY statements to also put these in the appropriate locations).