Fish, tomato and olive stew on creamy mash

Ingredients

• 1 tablespoon rice bran oil
• 1 red onion, chopped
• 4 clove garlic, thinly sliced
• 1/2 cup (125ml) dry white wine
• 2 400 g cans cherry tomatoes
• 1 teaspoon white sugar
• 800 gram floury potatoes, such as sebago, peeled, chopped
• 40 gram butter
• 1/4 cup (60ml) milk, warmed
• 1/3 cup (50g) green olives
• 700 gram firm white fish fillets, skin removed, cut into 3 cm pieces
• basil leaves, to serve