By William Lander, Shaun Searley and Daniel Morgenthau
The ultimate picnic sandwich: perfectly roasted ham under a sweet mustard crust and unctuous fat, offset by the coarse, sharp bursts of mustard seeds. We make our own mustard in-house, using Kernel beer, but any high-quality grain mustard will do.
Cut the buns in half and generously butter both halves. Spread the mustard on the bottom half of each bun.
Thinly slice the ham, either using a meat slicer or as thinly as you can by hand. Divide the ham between the buns and season with salt and pepper. Top with a big pinch of watercress and sandwich together.