Scrub and thinly slice the artichokes. Melt the butter in a large saucepan and very gently fry the artichokes, stirring, for 10 minutes until beginning to soften.
Add the pearl barley and cook, stirring, for 2 minutes. Stir in the wine and cook quickly for 2–3 minutes until the wine has been absorbed. Gradually add the hot stock to the pan, a ladleful at a time, and cook, stirring frequently, until each ladleful has been absorbed. Continue to cook, adding a ladleful of stock at a time and stirring frequently until each ladleful has mostly been absorbed before adding the next. This should take about 20–25 minutes, by which time the barley should be tender but retaining a little bite. Add a little more stock if needed.
Stir the mascarpone, herbs and lemon rind into the risotto and cook for a further 2 minutes. Season to taste with salt and pepper and serve sprinkled with grated Parmesan.