Place feta and garlic in the bowl of a food processor fitted with the steel blade and pulse until just combined. Add 1/3 cup (80ml) olive oil, lemon juice, 1/2 teaspoon salt and 1/4 teaspoon cracked black pepper and process until smooth.
Heat 2 teaspoons oil in a large frying pan over high heat. Cook tomatoes, without stirring, for 1 minute or until they blister and lightly char on the bottom. Gently stir and repeat until blistered on most sides (they should be lightly browned in spots, but not falling apart). Transfer to a bowl and season with salt and pepper. Drizzle with 2 teaspoons olive oil and set aside.
Combine dukkah and pistachios in a small bowl. Slice avocado into 8 pieces, and then combine with 1 teaspoon olive oil in a bowl and gently toss to coat. Sprinkle avocado with dukkah mixture.
Toast or grill sourdough on both sides until golden. Spread each slice with a thick layer of whipped feta, then top with blistered tomatoes and dukkah-coated avocado. Sprinkle with basil and season with salt and cracked black pepper. Drizzle with remaining olive oil to serve.
Dukkah is an Egyptian blend of nuts, seeds and spices. It is available from the spice section of most supermarkets or delicatessens.
Crush pistachios using the back of a large spoon or knife.