French Onion Soup with Cheesey Croutons

1 T olive oil
50g butter
1kg brown onions, thinly sliced
1 t brown sugar
2 T plain flour
1 L beef stock
½ C dry white wine
Salt and pepper
2 small bake-at-home rolls, 1cm thick slices
2 slices cheese
Heat oil and butter and cook onion 10 mins until soft. Add brown sugar, cook 3-4 mins until sugar dissolves and onion golden. Add flour and cook stirring 1-2 mins until foaming. Remove from heat. Gradually add stock and wine and stir until combined. Return to medium heat and cook stirring 5 mins until thickens slightly. Season. Preheat grill, grill bread slices 2-3 mins each side until toasted. Divide cheese among bread slices and melt under grill. Serve soup into bowls, top each with 2 croutons.