Cornish crab bisque with lemony croutons

Name: Cornish crab bisque with lemony croutons
Ingredients: 2 tbsp olive or rapeseed oil, plus a little to serve; 1 onion, chopped; 1 fennel bulb, fronds picked and reserved, bulb chopped; 1 carrot, chopped; 2 bay leaves; 1 garlic clove, crushed; 1 tbsp tomato purée; 200g crabmeat (half brown meat, half white meat) or 1 medium whole crab; pinch of saffron; 3 tbsp brandy; 1l good-quality fish stock (or make your own if using a whole crab - see tip, below); 100ml double cream; zest 1 lemon, plus a squeeze of juice; 2 slices white bread, crusts removed, cut into croutons