Trim stalks from artichokes to 2cm, snap off tough outer leaves to reach tender pale leaves, cut 3cm from top of each artichoke and place in a bowl with lemon juice and 2 litres of water. Remove from acidulated water, one at a time, and peel outside of stalk, cut into quarters and, using a teaspoon, scoop out hairy choke and discard, placing artichokes back into water as you go.
Finely slice artichokes using a mandolin over a bowl containing vinegar. Add oil, season to taste with sea salt and ground black pepper, toss to combine. Add lettuce, fontina and chives to artichoke mixture, and adjust seasoning to taste.