Nibblous | parsnip, rhubarb & ginger soup

Ingredients

• 50g butter
• 450g parsnips, peeled and roughly chopped
• 225g rhubarb, washed and roughly sliced
• 1 medium onion, finely sliced
• 2 tsps fresh ginger, grated
• 1 tbsp plain flour
• 850ml chicken stock
• 2 tsps light brown muscovado sugar