Put the egg yolks into a bowl and whisk. Pour in the condensed milk, egg, yolks, mashed strawberries, and sugar into a saucepan. Cook on medium-low heat and stir the whole time. This should take about 15 minutes and be thick. Put in the fridge to cool.
For the cupcakes:
Combine the butter, eggs, sugar, lemon zest and juice, sour cream, milk, and mix.
Grab a different bowl and sift the two flours. Add the baking powder and salt and mix.
Put the flour mixture into the other mix a bit at a time and mix until well blended. Mix on high for 1 minute.
Fill cupcake liners 3/4 full. Put in the oven and bake for 15-20 minutes at 350 degrees.
Remove and let cool on a wire rack.
For the frosting:
Blend the cream cheese and butter until smooth. Add in the pureed strawberries and vanilla. Add in the powdered sugar in small batches and blend. Frosting should be thick to pipe on the cupcakes.
Put the bowl in the fridge and cover it with foil until you're going to use it.
Once the cupcakes are done cooling, take out the center of each cupcake with a corer. Put in a teaspoon of the strawberry filling and put a whole strawberry on top.
Then, take the frosting out of the fridge and put it in a pastry bag with a star tip. Pipe on the frosting and top the whole cupcake with a strawberry.