Preheat the oven to 200°C. Remove the lamb from the fridge and allow to reach room temperature. Rinse the herbs and place in a blender with the garlic, lemon zest and olive oil. Blend until mixed (it does not have to be very fine).
Prepare the crust. Mix the garlic, ground almonds, lemon juice, green olives and 30ml of the herb filling. Add olive oil and season with salt and pepper.
Butterfly the leg of lamb if not already done by your butcher, and spread the herb gremolata thickly over the meat.
Roll up and tie up with kitchen string. Place in a roasting pan and cover with the crust mixture.
Roast for 45 minutes, or until the lamb is cooked but still pink inside. Set aside to rest.
While the lamb is roasting, mix the ricotta, anchovies, lemon zest and juice, parsley and mint. Season with salt and pepper. Carefully stuff the pumpkin flowers with the mixture and close the ends gently. Mix all the flower batter ingredients with a fork until combined. Add the sparkling water a little at a time so that the batter is of a slightly thinner consistency than that of a pancake batter.
Warm a medium-sized pot with vegetable oil for deep-frying. Dip the stuffed flowers carefully into the batter and then place in the hot oil. Cook just until the crust turns crisp.
Remove and place on paper towel to absorb the excess oil. Serve warm with slices of lamb.