Tuna pepper steak with spinach and anchovy sauce from Spice by Christine Manfield

Ingredients

• 3 bunches spinach, stems removed
• 50 g unsalted butter
• olive oil
• coarsely ground black pepper
• 6 x 150 g tuna steaks (2 cm thick), cleaned
• 250 g unsalted butter, softened
• ¼ teaspoon freshly grated nutmeg
• ½ teaspoon freshly ground black pepper
• ½ teaspoon sea salt
• 8 cloves garlic
• 1 tablespoon chopped flat-leaf parsley
• 30 ml strained lemon juice
• 10 anchovy fillets
• 1 teaspoon strained lemon juice
• 25 ml sherry vinegar
• 6 anchovy fillets, chopped
• 2 large (61 g) eggs
• 300 ml extra-virgin olive oil
• ½ teaspoon freshly ground white pepper