To make the condensed milk dressing, combine all of the ingredients in a bowl. Taste and season with more salt and pepper if necessary.
Drain the lettuce, remove any mangy outer leaves, trim the base of the core so it’s flat, and put the whole head in a salad spinner. Give it a few bursts in the spinner to dry as much as possible, and dry well on a clean tea towel, then transfer to the fridge to keep chilled until ready to get the party started.
To serve, use a sharp knife to slice the lettuce into four thick horizontal slabs, keeping the lettuce’s structural integrity as secure as possible. You’ll essentially be rebuilding the lettuce, drizzling the dressing generously in between like mortar.
Place the base of the lettuce on a round platter and drizzle with a generous amount of the dressing. Using a microplane, grate an egg over and sprinkle with some chives. Top with the next slice of lettuce and add dressing, egg and chives as before. Continue these layers until the top is popped back into place.
Finally, grate the last egg over the top for the crown and sprinkle with the remaining chives. Slice into wedges to serve at the table.