Heat the butter in a large saucepan, add the onion and garlic and gently fry 4 to 5 minutes or until softened.
Stir in the flour, nutmeg, cinnamon and pumpkin; cover and cook gently for 5 to 7 minutes, stirring occasionally.
Pour in the chicken stock, orange juice and brown sugar.
Cover and bring to a boil, then reduce the heat and simmer for 20 minutes, until the pumpkin has softened.
Meanwhile, make the croutons.
Heat the oil in a frying pan, cut the whole wheat bread sliced into cubes and fry gently until just brown - add the sunflower seeds and fry for an additional 1 to 2 minutes; drain the croutons and sunflower seed on a papper towel.
Return to soup.
Pour only half of the soup mixture into a blender or food processor and process until smooth; return soup to the saucepan.
Season well with salt and freshly ground black pepper, if desired and heat through.
Serve the soup hot garnished with a few of the croutons and sunflower seeds sprinkled over the top.