Heat one tablespoon of butter over medium heat in a Dutch oven. Add the potatoes, cabbage, carrots, Guinness and all the seasonings, salt through marjoram. Cover and simmer for 20 – 25 minutes, stirring occasionally, until potatoes are fork tender.
Meanwhile, brown the ground beef in a small skillet.
Remove lid from Dutch oven and stir in the ground beef. Allow to simmer uncovered for about 5 minutes. Stir in the mustard and cheddar cheese and stir until cheese is completely melted. Remove from heat and allow filling to cool. Filling can be made up to one day ahead and stored in the refrigerator, in an air-tight container.
Unroll the pie crusts and cut each round into four pie shaped wedges. Roll each wedge so it is thinner and larger. Place about 1/2 cup of the filling off-set in the center and fold the crust over the filling, making a pie shape. Crimp the edges to seal in the filling.
Brush the hand pies with the remaining melted butter and sprinkle with a bit of additional caraway seeds if desired.
Preheat oven to 450 degrees. Place hand pies on a sheet pan lined with a silicone baking mat or parchment paper. Bake for 20 minutes. Serve warm.