Preheat the oven to 375°F (190°C). Place the artichokes on a baking tray lined with aluminum, drizzle with the olive oil and season with salt and pepper. Put in the oven for about 30min until soft and cooked through.
Put the walnuts on a baking tray. Pop in the oven for about 5min until golden. Take out and leave to cool. Chop roughly.
Prepare the seasoning by mixing together the mustard, the vinegar and olive oil. Toss with the artichokes.
When the artichokes are cooked and warm, prepare 2 plates with greens on the bottom. Spoon the artichokes on top and add the walnuts and ricotta on top. Serve straight away.