It may take time to make as the dough needs to be rested at a certain after it has been formed and after it has been shaped into the tart mold, then baking the tart shell and cooling it down before adding the filling. But I just need to make this tart. And the cool weather is perfect for it. The dough is forgiving.
Actually, this onion tart is not for me. Every Tuesday night, we have Bible studies. J and I have our own group while J's aunts have another group. We do our Bible studies on the same night but separately. Before we start, we have dinner first. Each member would voluntarily bring food for everyone. That's how we do it ever since. Now that we're married, J doesn't have to buy food anymore, I cook dinner instead. For J's aunts' Bible study group, I would only prepare snacks and I think this onion tart is a perfect choice. I can prepare it one day ahead, chill it and serve it the following day at room temperature or even slightly warm.
Caramelized Onion Tart with Emmenthal Cheese and Bacon
Crust: 200 g all purpose flour 120 g unsalted butter, cold 1/4 tsp fine sea salt 3-4 tbsp cold water
Filling: 4 tbsp olive oil 700 grams white onion (around 6 onions) 2 sprigs fresh thyme salt and white pepper to taste
1 tsp balsamic vinegar 1 T water 90 grams picnic bacon 85 grams Emmenthal cheese 3 whole eggs 250 ml sour cream (or 125 ml each of milk and cream)
To start the crust, make sure all the ingredients are cold before making the dough. Combine the salt and the flour and grate the butter using the large hole of a box grater. Toss the butter and flour, then rub the butter and the flour by pinching it in between your fingers until the dough looks like a size of a couscous. Add the water, a bit at a time to form the dough. Transfer the dough onto a work surface and bring the dough together by kneading it light. Wrap and flatten the dough and let it rest in the chiller for around 30-45 minutes.
To roll the dough, dust the work area and the dough with flour. Roll the dough out to 1/4" - inch thickness. Transfer to a greased 9"-inch tart plan. shape and place into the chiller for another 45 minutes to an hour.
Preheat your oven to 425° degrees Fahrenheit (or 220 degrees Celsius)/
To start the filling, thinly slice the onions. Heat a large fry pan over high heat. Add the oil and onion and sweat the onions for about 5 to 10 minutes until they are wilted. Reduce the heat and cook for another 15 minutes or so, stirring occasionally. Remove the thyme leaves from the stem and add to the onions. Once the moisture has evaporated, season with salt and stir the mixture every 20 seconds as the caramelization will occur quickly. This will ensure even cooking. Off the season, deglaze with the balsamic vinegar and water. Scrape to clean the bottom of the pan. Season with salt and white pepper and set aside to cool. Meanwhile, cut the bacon into lardons and cook over medium heat for 7-8 minutes until golden brown.
Poke the holes into the dough with a fork. Line the dough with a parchment paper and add dried beans to add weight to the dough. This will prevent the dough from puffing up. Bake the dough for 20 minutes until the side crust is lightly brown. Remove the parchment paper and the dried beans and bake for another 15 minutes until the crust is cooked. Allow to cool down slightly before adding the filling.
While the crust is baking, grate the cheese, gather the eggs and the sour cream.
To finish the tart, turn the heat down to 350 degrees Fahrenheit or (175 degrees Celsius). In a large bowl, combine the cheese, the eggs and the sour cream, add the caramelized onions and the bacon, season with salt and white pepper. Transfer the mixture on the cooled crust and spread it out evenly. Bake for appromimately 30-45 minutes or until the top is set and golden brown. Allow to cool down before removing the pan. Slice and serve.