1Line the roasting pan with baking parchment paper.
2Rinse the cavity of the snapper under cold water and pat dry with paper towel. Make 3 shallow cuts into the thickest part of both sides of the fish.
3Remove the fronds from the fennel and set aside. Using a mandolin, thinly slice the fennel bulbs. Fill the cavity of the snapper with sliced fennel, lemon and herbs then lay the remaining over the bottom of the lined roasting pan.
4Season both sides of the fish with salt and pepper. Place the snapper over the fennel mixture in the roasting pan.
5Put the pistachios, fennel fronds and 2 tablespoons of oil in a food processor. Process for 15-20 seconds until chopped with some larger nuts remaining. The mixture should just hold together. If too dry, add a little more oil and pulse again.
6Press the pistachio mixture over the top of the fish to create a crust. Drizzle with the remaining oil.
7Insert the wire rack into the bottom shelf position. Preheat the oven. Select BAKE/ CONVECTION/350°F/35 minutes.
8Once preheated, put the snapper in the oven and bake for 35 minutes.
9Remove the snapper from the oven. Using the tip of a knife, make an incision near the head of the fish into the flesh. The flesh should be white, tender and coming away from the bone and the crust should be firm.
10Transfer the snapper and fennel to a serving platter. Serve with aioli and lemon wedges.