Heat 40ml oil in a large saucepan over medium-high heat, add onion and garlic and stir occasionally until very tender (6-8 minutes), add anchovies and chilli and stir until anchovies dissolve (1 minute). Add tomatoes, season to taste and simmer until thick (6-8 minutes).
Meanwhile, heat remaining oil in a separate large saucepan, add wine and mussels, cover and shake pan occasionally until mussels open (3-4 minutes). Strain mussel liquid into tomato mixture, and when cool enough to handle, remove half the mussels from their shells (discard shells) and set aside.
Meanwhile, preheat your grill to high heat. Drizzle bread slices with oil and toast, turning once, until golden. Rub with cut-side of garlic, season to taste and keep warm.
Add mussels to tomato mixture, simmer until warmed through, stir through parsley, scatter with basil and serve hot with garlic bruschetta to the side.