Macarons with Purple Plum Ganache and Plum Butter Filling

I made the shells with some purple swirling color but I think the reddish purple shade would be the best fit for the filling.  Bake these at lower temperature for better shade of purple.  I have not been tasting the real macarons in Paris but per macarons experts described in their cookbook:  the shell should be crisp but soft and slightly chewy inside.  If you like drier and crunchier like meringue bake a few minutes longer.

We need 1 recipe for macaron shells, post in Lemon Macarons and 1/2 cup plum butter.  The plum butter here has much less sugar than other recipes and will balance well with the sweetness of white chocolate.  If you like thicker filling, double the recipe.

Shells:

212g Almond flour
212g Powder sugar
A few drops of reddish purple food color gel

 82g & 90g egg white

236 g granulated sugar plus a pinch for egg whites
2/3 cup water

Following the instruction in Lemon Macarons for the shells but bake it at 300 oF convection oven for 14-15 minutes. or 300 oF convention oven for 18 minutes. 

Filling:

1 pound of ripe, soft purple plums (about 14-16 small purple plums)
1/4 cup granulated sugar

6 oz white chocolate
1/2 teaspoon salt
A few Tablespoons of heavy whip cream to thin out the filling if needed (optional)

1.  Wash and remove the pits with your hands, keep the skin.  Put plums in a medium sauce pan with sugar and crush them with hands.  Bring the mixture to a boil over medium high heat.  Reduce the heat to medium, stir occasionally until the skin is really soft and releasing a beautiful reddish purple color about 15 minutes. Pass  the mixture through a food mill or a coarse sieve set over a metal/glass bowl to remove the skin.  Return the mixture to the sauce pan, bring it back to a boil.   Reduce heat down to low, simmer, uncovered and stir frequently (#2-2.6 setting on my stove) the mixture will be thicken about 35-40 minutes.  Keep stirring constantly near the end. When the mixture start leaving a  solid trace at the bottom when you made a line with a spoon and drip in big chunks from the spoon.  Make about 1/2 cup plum butter.  Remove from heat.
2.  Stir a few times to reduce the steam, then add white chocolate and stir until chocolate melt and blended well with plum butter. This will be thicker when it cools down.  Cover tightly and chill in the fridge if not using right away.  If it becomes too thick to pipe, add some heavy cream and whip it to piping stage. 

*Note:  

• I found a better fit for the shell color: Wilton's burgundy and violet , if you agree?