*You will add some blueberry and some strawberry filling from above
*You can make berry fillings ahead of time or right before starting the cupcakes. If making berries ahead of time, place the fillings in separate jars with a lid and keep in the fridge until ready to use.*
In a small sauce pot, over medium heat, combine blueberries, lemon juice, and sugar. Cover and bring to simmer. Take off the lid and let the berries simmer for 7-10 minutes, stirring often.
Follow the same process for strawberries. In a small sauce pot, over medium heat, combine strawberries, lemon juice, and sugar. Cover and bring to simmer. Take off the lid and let the berries simmer for 7-10 minutes, stirring often.
Puree strawberries and blueberries (separately). Transfer into two separate small jars and set aside until ready to use.
Follow package instruction to prepare the cupcakes.
Let cupcakes cool completely.
Beat butter and cream cheese together, on medium-high speed, until smooth, about 2 minutes.
Lower the speed to low and beat in powder sugar and vanilla.
Turn up the speed back to medium-high and beat for a couple more minutes, until the frosting is light, smooth and fluffy.
Take out half the frosting.
Whisk in 1 1/2 Tbsp of blueberry filling to one half and 1 1/2 Tbsp of strawberry filling to another half.
Fill two separate piping bags with blueberry and strawberry frosting. Cut off tips about ¼ inch wide and add them, side by side into one piping bag, fitted with a frosting tip. Tie a rubber band on the end of the piping bags to keep the frosting in. (You may need to refill the piping bags a couple of times.)
Using a small cookie dough scoop (or a melon baller), scoop out some of the cupcake on top and then, fill each cupcake hole with a little over a teaspoon of strawberry or blueberry filling.
Frost each cupcake with prepared blueberry/strawberry frosting.