For the tapenade, blend all of the ingredients except for the mayonnaise together until smooth. Stir in the mayonnaise.
For the arancini, melt the lactose free butter in a large heavy-bottomed saucepan. Add the rice and cook for 2-3 minutes on a low heat. When the rice starts to become a little translucent around the edges, add the wine and cook for another minute.
Add a ladleful of warm stock and stir well. When the stock has almost been absorbed, add another ladleful. Continue adding more stock until it has all been added and the rice is cooked.
Beat the egg in a bowl, sprinkle the rice flour onto a plate. Roll the rice into small balls, then dip into the beaten egg and dredge in the rice flour.
Half-fill a deep, heavy-based saucepan with vegetable oil and heat to 170C/325F (check using a digital thermometer). (CAUTION: Hot oil can be dangerous. Do not leave unattended).
Deep-fry the arancini for 3-4 minutes, or until golden-brown. Remove from the oil using a slotted spoon and set aside to drain on kitchen paper. Serve the arancini with the tapenade.