Melt butter in a medium sized saucepan. Add onion and salt, cook over medium heat; 10min, stirring occasionally.
Add mustard and thyme; stir and cover. Continue to cook very slowly; 25min, onion will be super soft and simmering in its’ own liquid.
Add water and pepper. Simmer further 10min.
Serve topped with bread and cheese, see below.
Divide soup evenly across 4 small oven proof bowls.
Top each with 1 slice of bread and 1 slice of cheese.
Place soup under the grill, heated to high (or top shelf of an oven pre-heated to 180°C) until cheese is melted. Remove from grill using oven proof gloves.
Serve hot.
Top Tip:
Try using different low protein cheeses if preferred. Mozzarella and Pizza are also full of flavour.
This recipe has been specifically designed for a low protein diet. Refer to labels for allergen and other product information.