Onion Tart with Mixed Greens

This recipe is a combination of two great French foods: pissaladierres and gallettes.  It is topped with caramelized onions like a pisaladierre, a type of pizza popular in southern France that is topped with caramelized onions, anchovies, and olives.   However this is not made with pizza dough like a pisaladierre but instead rests on a flaky pastry crust  like a galette, which is a flat, free-form, rustic tart.
This tart is baked and then topped with a salad of mixed greens so it is a complete meal all in itself and the flavors all mingle really nicely together this way.  The fact that this is a free-form tart is a great way to get around not having a tart pan and the presentation is really nice!  This recipe makes two of the tarts shown in the picture.  If cut into quarters, they would serve eight as an appetizer or a light brunch.  If serving for an entree, cut each in half to serve four.

Onion Tarts with Mixed Greens
Recipe adapted from Williams-Sonoma Kitchen

INGREDIENTS FOR THE TART DOUGH:

• 2 cups all-purpose flour
• 1/2 tsp. salt
• 1/2 tsp. sugar
• 12 Tbs. (1 1/2 sticks) unsalted butter, cut into 1/2-inch cubes
• 6 to 7 Tbs. ice water

INGREDIENTS FOR THE FILLING:

• 5 Tbs. olive oil
• 4 yellow onions, thinly sliced
• Salt and freshly ground pepper, to taste
• 3 garlic cloves, minced
•  1 1/2 tsp. dried thyme
• 2 Tbs. minced fresh flat-leaf parsley
• 4 tsp. balsamic vinegar
• 1 egg, lightly beaten
• 4 oz. mixed salad greens
• 2 oz. goat or feta cheese, crumbled

TO MAKE THE TART DOUGH:

In the bowl of a food processor, pulse to combine the flour, salt and sugar. Add the butter and pulse until pea-size crumbs form. Add the water 1 Tbs. at a time and pulse, adding more water as needed until the dough just starts to come together. It should be moist but not sticky.

Turn the dough out onto a lightly floured surface, divide into 2 balls and shape each into a 5-inch disk. Cover separately with plastic wrap and refrigerate for at least 1 hour.

On a lightly floured surface, roll out each dough disk into a 12-inch round about 1/8 inch thick. Transfer each round to a parchment-lined baking sheet and refrigerate for at least 30 minutes.

TO MAKE THE FILLING:

Preheat the oven to 400 degrees.

Once the dough is rolled out and in the refrigerator, begin chopping the onions. In a non-stick sauté pan over medium-high heat, warm 3 Tbs. of the olive oil. Add the onions, salt and pepper and cook, stirring occasionally, until caramelized, 15 to 20 minutes. Add the garlic and cook for 1 minute more. Add the thyme, parsley and 2 tsp. of the vinegar and cook, stirring occasionally, until most of the liquid has evaporated, about 2 minutes. Remove from the heat and let cool slightly.

Spread half of the onion mixture on each dough round, leaving a 1-inch border. Fold the dough up and pinch together at 2-inch intervals. Lightly brush the top of the dough with the beaten egg. Bake the tarts until the crusts are golden, 30 to 35 minutes. Transfer the baking sheets to wire racks and let the tarts cool for 10 minutes.

In a bowl, toss the salad greens with the remaining 2 tsp. vinegar, the remaining 2 Tbs. olive oil, salt and pepper. Top the tarts with the salad, dividing evenly, and sprinkle with the cheese.