First take your cream cheese, and get it to room temperature. Then add in your feta and chopped up sun-dried tomatoes. Combine it until you get all the ingredients well integrated. I like to roll mine into a tube shape. You can easily do this by wrapping the mixture in plastic wrap.
To make the burgers take the amount of hamburger meat you would typically use to make one burger and split it into two. Flatten these two halves and make a skinnier burger. Slice off part of the mixture of the cream cheese-feta-sun dried tomato mixture and place it on top of one of the skinny burgers and then place the other burger on top. Then seal the sides. When it is completed then cook your burger to your liking. We like to cook ours in a cast iron skillet, it seals in the flavor well and makes the burger yummy!