1. Prepare the chicory, cutting out part of the bitter base. Rinse, dry thoroughly and cut lengthwise in half (if the heads are very fat, cut lengthwise into quarters).
2. Divide the butter in half between 2 frying pans or very wide, shallow saucepans with tightly fitting lids and heat until it foams.
3. Add the chicory pieces, spreading them out in a single layer in the hot butter, and fry over a moderately high heat until lightly browned. Turn carefully and brown the other side.
4. Add half the stock to each cooking receptacle, cover tightly and reduce the heat to low. Simmer for 5 minutes.
5. Mix the sugar with the strained juice of the 2 lemons, remove the lids and sprinkle the sweetened lemon juice all over the chicory. Turn up the heat a little to reduce the lemon juice and liquid and caramelize slightly, loosening the chicory gently with a non-stick spatula if they show signs of sticking.
6. Sprinkle with a little salt and freshly ground white pepper and serve.