My First Stuffed Burger

I'm not an expert at making hamburgers. I tried one time in my mid-teens, and all of my patties puffed up like little meatballs instead of flat, bun-worthy burgers. However, whilst on vacation I was flipping through a magazine and found an article on different types of burgers. Square ones, sliders, stuffed- you name it. So I got on this burger kick and set out to get my burger skillz up to par. Or at least to the place where my patties were flat and not pink inside.
I also tried some of the variations- stuffed being one of them. I don't think it turned out too bad, though the finished product separated a little bit and looked like a burger-sandwich. Like the StrawBurger, this one was eaten paleo style with tomato garnish, but featuring cheese and pesto. It was incredible!