Step 1

Preheat oven to 400 degrees.

Step 2

In a medium bowl add 2 T of mustard and a generous pinch of salt to the ground beef. Using your hands, mix gently until everything is thoroughly combined.

Step 3

Roll meat into very small balls, roughly 1 1/2 inches across and set on a rimmed cookie sheet. (I got 16 out of my batch.) Press each ball down gently to slightly flatten .

Step 4

Bake for 10 minutes, remove and lay a small piece of cheese over each burger. Return to oven for 1-2 more minutes until cheese is melted and burgers are cooked through.

Step 5

While the burgers are cooking, spread mustard on buns (if you like), and cut into 1-inch pieces. Prepare remaining ingredients and have everything ready when the burgers come out of the oven.

Step 6

Assemble burgers on toothpicks by stabbing some bread (mustard side down), then lettuce, then tomato, then a burger, then the other piece of bread (mustard side up). When you put them on a serving dish, press everything down a bit -- that will help them stand up.