Grilled Beefsteak tomatoes with chili, garlic and ginger

Ingredients

• 75ml olive oil
• 2 long red chilies, cut into 0.5cm-thick rounds or flakes of hot peppers
• 4 garlic cloves, peeled and very thinly sliced
• 4 cm piece fresh ginger, peeled and cut into thin julienne strips
• 20g coriander stalks, cut into 4 cm-long lengths, plus 5 grams coriander leaves, to garnish
• 1.1kg beef tomatoes (ie, 4-5 tomatoes), cut width ways into 1cm-thick rounds
• Flaked sea salt and black pepper
• 1½ tsp black mustard seeds, lightly toasted