Make the dough

1. Preheat the oven to 325 F (160 C).
2. Lightly spray an 8″x8″ pan with cooking spray, and then cut a piece of parchment

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   to line the bottom and sides of one side. Spray over the top of this piece of parchment

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   , then cut another one to go across the remaining 2 sides of the pan.
3. Beat the butter with the sugar and vanilla paste in a mixer until smooth.  Add in the flour and mix just until the flour disappears.
4. Line a sheet tray with a piece of plastic wrap.  Divide the dough into thirds.  Press each third into a compact ball.

Color the doughs

1. Place one of the dough pieces on a piece of plastic wrap.  Press down the dough into a thin disc and then sprinkle it with the matcha powder.  Use the plastic wrap to fold the dough over onto itself until the color of the matcha is well-distributed.  Try to smear the powder into the dough so that it gets absorbed in the least amount of work.  Nobody wants tough shortbread!
2. Repeat the same process with another piece of dough with the strawberry powder.  If your powder seems chunky, press it through a small strainer to remove any lumps right over the dough.
3. After you have all 3 colors of dough ready to go, divide each color into 3 pieces.  Roll each piece of dough on a piece of plastic wrap into an even log 8″ long.  Use the pan to help you gauge how long your dough needs to be. 

Prepping and baking the shortbread

1. Once you have rolled all the dough, lay the pieces into the pan in the order red-white-green, red-white-green, red-white-green.  Place a piece of plastic wrap over the pan and use a small roller or your hands to press the dough into the corners.  Try to press only along the stripes so as not to obscure the pattern.
2. Cut the dough in the pan across the stripes into 12 pieces with a bench scraper

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   .  Also cut each line vertically after each series of 3 colors.  You should have 36 total shortbread fingers.
3. Take a fork and poke down to the bottom of the pan roughly in the middle of each shortbread finger.
4. Bake the shortbread for 40 minutes until it barely springs back when you touch the middle.

Finish the shortbread

1. Immediately after the baking is finished, use your bench scraper

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   to cut along the same lines you cut earlier.  Let the shortbread sit in the pan until completely cool.
2. Store the shortbread at room temperature in an airtight container for up to 1 week.  To freeze the shortbread, take out the whole parchment

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   sling and place it in a plastic bag for the freezer.  Wrapped up this way, shortbread fingers will easily keep in the freezer for 3 months.