Almond shortbread with half almond meal

My almond shortbread cookies have been very successful so far. So I am experimenting with variations of it. In this experiment, I increase the almond meal to flour ratio to 1:1 without changing any other ingredients.

Recipe: Almond shortbread with half atta flour and half almond meal (this recipe makes double portion size)

Ingredients:
- 1 cup Trader Joe's almond meal
- 1 cup Golden Temple atta flour
- 4 TB cornstarch
- 1 tp table salt
- 12 TB butter
- 2 TB dark brown sugar
- 3 TB white sugar
- raw almonds, soaked and sliced for topping

Procedure:

1. Mix flour, almond meal, cornstarch, sugars and salt in a medium bowl.

2. chop butter into small pieces. Use a fork to soften the butter, until it forms a smooth thick paste. 

3. Add the softened butter by spoonful into the flour mixture and use hand to mix them together until they are just incorporated to form one ball of dough. 

4. Make small 1.5" balls out of the dough. Press each down into a mini-tart mold.

5. Place a slice of soaked almond on each piece of dough, pressing it down.

6. Preheat oven to 300F. Place the tart tray in the oven and bake at 300F (or slightly lower temperature such as 275F) for 20-25 minutes, until the top is lightly brown.

7. Allow to cool in oven for several hours so that the shortbread becomes crispy.

Results:

3:33pm, soft and moist final dough:

3:43pm, dough balls ready to bake:

4:03pm, shortbread baked 20 minutes:

4:18pm, top of the shortbread:

4:18pm, side of the shortbread:

Observations:

1. For some reason yet unknown to me, the dough becomes really easily incorporated in this dough. In fact,  because of such ease, I knead the dough rather rigorously for a while.
2. Eventually, the dough is so soft and pliable that I decide to chill it for a while before molding into dough balls. 

3. When just baked, the resultant shortbread seem to be softer and more puffy than my previous experiment with only 1/3 almond meal. I continue keeping the shortbread in the oven at 150F. After an hour or two, it has hardened completely. With longer low-heat baking, the shortbread also becomes darker in color.

This experiment makes me wonder how the ingredients affect the characteristic of the shortbread or cookie. Then I find some helpful resource (source: Understanding Food, Principles and Preparation, reporting results from: Fine cooking, 1998)

For puffy, soft, pale cookies:

- cake flour (low protein, acid) gives more steam and puff, ; less browning

- shortening (high melting point) gives less spread

- all brown sugar (hygroscopic, acid) gives soft and moist; less spread when used with egg

- egg gives moisture for puff; less spread with acidic ingredients

For thin, crisp cookies:

- all-purpose flour (high protein) gives browning

- butter (protein) gives more spread; browning

- baking soda (alkali) gives browning

- corn syrup (glucose) gives browning; crisp

- white sugar (sucrose) gives crip

- no egg gives no puff; more spread