Ardennes chicory soup (soup a l`ardennaise)

1 lb chicory (Belgian endive)
salt
2 ea leeks, white part only
pepper, white
1/4 c butter
2 ea egg yolks
2 sm potatoes, peeled, diced
2 1/2 c milk
2 T chives, chopped fine

1. Remove and discard core from each chicory head - cut remainder into 1/4 inch slices. Cut leeks in 1/4 inch pieces. Melt butter in a large saucepan. Add sliced chicory and leeks - saute 2-3 minutes. Add potatoes and milk. Season to taste with salt, white pepper. Bring to a boil, stirring occasionally. Cover and simmer 45 minutes - until potatoes are tender.
2. In a small bowl, baat egg yolks with half and half. Stir in 1/4 cup hot milk mixture. Stir egg-yolk mixture into remain milk mixture. Stirring constantly, cook until slightly thickened. Pour into a tureen - or serve in individual bowls. Garnish with chives. Serve immediately.