One of my favorite filling is the Ganache. You only have to do this one day ahead. This sounds odd, but it is worth for a firm filling and you need not more than 15 min. to do.
200gr. white chocolate – with 90 gr. cream
or 150 gr. milk chocolate – with 100 gr. cream
or 100 gr. dark chocolate – with 100 gr. cream
It depends whether you want to color your filling (then use the white chocolate).
Powdered food color
Chop the chocolate. Heat the cream up to 40°C +/- 45°C (105°F +/- 115°F) and take away from the heat. Put 1/3 of the chocolate into the cream and let melt. Bit by bit put in the rest. If necessary put the cream/chocolate mixture back to the heat – but take care, that it does not get too hot.
Work with a spatula until you have a homogenous mixture. If you wanna have a color put in the powdered food color into your melted white chocolate now. When it is colored fill into a small bowl. Cover with a foil (perforate with a needle to avoid condensate) and leave aside over night.
The next day blend the mixture with a handheld electric mixer until the volume improved and fill into your pastry.
If the mixture is too hard – use a double boiler to bring it to the texture you need for your pastry.
After filling the shells I return them into the fridge. I take them out aprox. 30 minutes before I wanna serve them.
If necessary and you don´t have the time the day before put the Ganache in the fridge for approx. two hours and blend it then.