Step 1

If possible, make the raspberry filling in advance! The extra time will allow the filling to thicken and develop its flavor.

Step 2

Place the frozen or fresh raspberries, granulated sugar, lemon juice and lemon zest, and 1/4 cup of water in a saucepan and heat over medium high heat.

Step 3

Stir the mixture until it begins to boil.

Step 4

Lower the heat to medium-low, and allow the filling to simmer for 10-15 minutes.

Step 5

Turn off heat and remove the pot from the stove. Pour the filling into a metal strainer suspended over a medium sized bowl, and push through using a rubber stapula. Use a decent amount of pressure to really get all the liquid through the sieve. You should be left with about 1/2 cup of seedy pulp.

Step 6

In a separate small bowl, make a slurry by combine the remaining 1/4 cup of water with the cornstarch. Stir until the cornstarch has fully dissolved into the water.

Step 7

Add this cornstarch mixture into the strained raspberry filling, and stir until it is incorporated.

Step 8

Rinse out your pot and pour the filling back into it (you don't want any residual seeds getting into the filling).

Step 9

Heat at a medium high heat, and be sure to stir constantly during this stage to prevent the filling from burning.

Step 10

Cook until the mixture begins to boil, then reduce the heat to medium low.

Step 11

Continue to stir, and cook for a few additional minutes.

Step 12

Turn off heat and pour the raspberry filling into a separate bowl to cool. Cover with plastic wrap and place in the fridge for at least 1 hour, or preferably overnight.