Slice off top end of strawberry so that the strawberry can stand on a flat surface. Then make a deep knife cut on top of strawberry. You want to make two cuts for each strawberry in the shape of an "X" or a cross. You want to cut about 3/4 of the way down, but not all the way. Use your finger to help separate the petal of the strawberries so that they open up enough for stuffing.
In a stand mixer, mix the mascarpone cheese, heavy cream and sugar until it is fully mixed and forms a whipped cream frosting look (it will probably curdle first before coming together).
Put mixture into a piping bag and pipe the strawberries. Top with blueberries.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.