Prepare strawberry cake according to package directions in a greased 9x13-inch pan.
In a medium mixing bowl, beat sweetened condensed milk, evaporated milk, and half and half.
Poke holes in warm cake and pour mixture over top. Cool cake completely, covering it and refrigerating it overnight.
Just before serving, beat heavy whipping cream, powdered sugar, and vanilla together until peaks form.
Spread mixture over top of cake and garnish with fresh strawberries.
Notes
After the cake is taken out of the oven, immediately poke holes in the cake using a chopstick, straw, or skewer.
Be sure to choose fresh, ripe strawberries as they will give the best flavor and presentation!
As you're pouring the tres leches mixture over the cake, take your time and make sure the mixture you pour soaks fully into the cake before adding more.