Belgian Endive & Cheese Tart with Walnuts

Frozen puff pastry (not to mention all the other ingredients) makes this dish rich and elegant, but it's very simple to make. A crisp green salad is all it needs to be a complete meal, and balances out the richness very well. It does well made ahead, so it would be good for entertaining, but it can't be made too far ahead, or the pastry will go soggy. It's not this recipe - that's a hazard of puff pastry generally. A couple of hours is good though.

You could also make small versions of this; it would make an excellent appetizer or hors d'oeuvre. In that case, though, I'd expect to use twice as much puff pastry as the total area covered with the filling would diminish every time you make the tarts smaller. Expect 18 (3 x 3 squares) or 32 (4 x 4 squares) little tarts. Baking time would be a few minutes less as well, so start checking them sooner. 

I dithered a bit about making this with blue cheese; if anyone ever tries that I'd love to know about it.
6 servings
1 hour 15 minutes - 45 minutes prep time 
plus allow some time to cool
Belgian Endive & Cheese Tart with Walnuts
Prepare the Belgian Endives:
4 medium (450 grams; 1 pound) Belgian endive
2 tablespoons unsalted butter
1 teaspoon sugar
salt & freshly ground black pepper to taste
Wash and trim the endives, and cut them in half lengthwise. 
Heat the butter in a skillet large enough to hold them in a single layer, and cook them over medium-high heat for 10 to 15 minutes, turning them over halfway through. Keep a lid on the skillet while they cook. As soon as they are turned over, sprinkle them with the sugar and season with salt and pepper.  

Once they are done, remove them from the heat and let them cool, at least enough to handle.
Make the Sauce:
1 tablespoon unsalted butter
1 tablespoon wheat flour
1 teaspoon Dijon mustard
3/4 cup whole milk or light cream
125 grams (4 ounces) cheese such as
   Gruyere, Gouda, Friulano - something tangy but melty
salt & freshly ground black pepper to taste
a few good grates of nutmeg
1 large egg 

Heat the butter, flour, and mustard in a saucepan and mix until they form a smooth paste; let it cook for a minute or two then mix in the milk or cream, a little at a time, to form a smooth sauce. Add the cheese, grated or cut in dice. Stir to melt it, and add the salt, pepper, and nutmeg. The amount of salt to add is going to depend very much on how salty the cheese is, but in general this dish calls for shakes of the salt shaker and not any kind of spoonfuls. 

When the cheese is melted, remove the pan from the heat. Allow it to cool enough that you can beat in the egg without the egg being in danger of cooking.
Assemble & Bake the Tart:
225 grams (8 ounces) frozen puff pastry, thawed 
a handful of walnuts
1/3 cup grated Parmesan cheese
Preheat the oven to 375°F. Roll out the pastry on a baking tray lined with parchment. Spread half of the cheese sauce over it, leaving an inch and a half to 2 inches all around. 
Slice the cooked pieces of endive, discarding the solid centres, and arrange them over the cheese sauce and pastry. Dot the remaining cheese sauce over them, and spread it out evenly.  Sprinkle with walnuts, and with the Parmesan cheese. Fold up the edges of the pastry to form low sides.

Bake for about 30 minutes, until set and nicely browned. Let cool to at least just warm, or to room temperature, before serving. 

Belgian Endive & Cheese Tart with Walnuts