Spinach potato soup with savoury egg custard

Savoury egg custard

• 4 eggs
• 100 g full cream milk
• ½ tsp salt
• 1 - 2 pinches ground nutmeg

Spinach potato soup

• 80 g brown onion, cut into halves
• 20 g oil
• 40 g celeriac
• 100 g carrots, cut into pieces (2 cm)
• 200 - 250 g potatoes, cut into pieces (2 cm)
• 80 g leeks, white part only, cut into slices (1 cm)
• 800 g water
• 1 heaped tsp Vegetable stock paste (refer to the recipe in The Basic Cookbook)
• ¼ tsp ground nutmeg
• 1 tsp salt, plus extra to taste
• ¼ tsp ground pepper, plus extra to taste
• 250 g fresh spinach leaves
  of 250 g frozen spinach leaves, defrosted
• 80 g thickened cream