Lemon Bars

This lemon bars recipe is from the "Ad Hoc at Home" cookbook, page 304.  The original Lemon bars recipe is called Lemon Bars with Meringue. 
In this Ad Hoc at Home cookbook, Chef Thomas Keller included several basics and important step-by-step techniques and illustrations.  Since I am a visual learner, the cooking illustrations help me a lot and motivate me to cook something beautiful and tasty, too.  So about a month ago,  I had my hands-on testing of the first recipe out of the cookbook - the buttermilk fried chicken recipe.  I was quite pleased with the result of my buttermilk fried chicken, then, I found out that it is served every other Mondays at the Ad Hoc Restaurant in Yountville, Calfornia.  I planned several visits to Ad Hoc in hope to taste the real buttermilk fried chicken by the true master chef, but I striked out three times - remembering the wrong date or wrong time of the day. I wound up at the Bouchon Bakery and purchasing pastries to comfort myself.  That's when I discovered the lemon tarts.  I fell in love with the Lemon Tarts.  The Bouchon Bakery's lemon tart is addictive?  It seems to have encoded something in my memory.  I keep on thinking about it and wondering how it is made.  How is the lemony custard so creamy and full of fresh lemon taste?  The tart shell is light and buttery.  The fork would cut right through the tart shell.   It motivated me to test the recipe in the Ad Hoc at Home cookbook.  Unfortunately, the local grocery did not carry pine nuts, so I decided to make the lemon bars.
Result:
While I have made lemon bars many times in the past and successfully, I am a bit disappointed with my lemon bars' appearance.  I used the exact same amount of ingredients, but the lemon bars turned out quite thin.
The crust:  I made sure to roll the crust's dough into 12-by-16" rectangle, but the crust turned out quite thinner than I am used to.  It seemed it did not have enough dough to be rolled out into reasonable 12-by-16" rectangle.  I was really over stretching it.  The thin crust did not hold the weight of the filling and broke as it is picked up.  Perhaps, it is not meant to be a finger dessert, I think so.
The filling:  The process of making this filling was very interesting.  The bain marie process solidified the liquidy lemon juice and eggs and sugar into a smooth and creamy, pastry cream like, custard.  It took me about 30 minutes, rather than the 5 minutes, to thicken it to the consistency of 'medium peak' beaten egg whites.  When the butter was added bit by bit, I was almost afraid that the mixture would turn soft, but it held the form.
The taste of the filling:   Of the 6 lemons I used, four are from my mother's lemon tree and two are from the store.  The acidity of the lemons from my mother was sweet and tart, but the sunkist's were sharp.  The filling tasted very tart and a bit too much.  It overpowered the creaminess.  The taste of lemon tart from Bouchon bakery is lemony and tart, but not leaving acidic taste at the back of the throat.  So, if this is my bakery product, I will make sure I know my supplier, the type of lemons I am getting, where the lemons are grown, and its tartness level.

Would I make the lemon bars again with the same recipe?  definitely, yes.  Until I get the same picture like lemon tarts and lemon bars as in the ones in the Ad Hoc at Home cookbook. 

 Once the filling has thickened and strained, poured over the crust, distributed and smoothed out, cover with parchment paper and plastic wrap and freeze it. 

Bring the frozen lemon bar sheet out and follow the instructions in the cookbook to lift it out of the sheet pan.  My method:  After loosening the lemon bar sheet all around the edges,  with the parchment cover and plastic wrap still on it, place the backside of another sheet pan on top of the covered lemon bar sheet and turn it over.  Then, press on the bottom of sheet pan to dislodge it.  Once it is out, put the backside of the sheet pan on the exposed crust and turn the lemon bars over to its right side up.  (I think I will bake it with the Silpat or silicone baking mat at the bottom of the crust the next time.) 
Carefully, remove the plastic wrap and parchment paper.  Cut into serving size.
Transfer them to the serving platter.
Sprinkle with powder sugar.  Or following the cookbook, pipe the meringue on top and roast it with the kitchen torch.

What did I learn from this process? 
It was a good idea that I was patient to have waited for the filling to thicken.  Using my gas stove and makeshift double boiler, cooking filling mixture for 5 minutes was not enough to thicken and to coat the whisk.  (*When thickened the mixture reached 180'F - is this too high?  I don't know, but the mixture is thick enough to coat the whisk and formed soft peak.)
Maybe - Use Silpat or silicone mat to bake the crust for easier removal of the lemon bars out of the baking sheet.
Maybe - Make double batch of the lemon filling for higher volume or use a bit smaller pan size than 12x16"
Use Myer Lemon or test with lemons that are less acidic.
While my eggs are fresh and organic, always use the most fresh eggs for this. 
Cut the bars smaller into bite size might have saved the crust from breaking if eaten as finger food.  I think, as illustrated in the cookbook, this lemon bars are supposed to be served over the plate rather than as the finger bars.  Perhaps, what I made is perfectly fine and the roasted meringue on top of the lemon bars would have made it look perfect(?).  Only the next test in plan will tell.