In a bowl, combine the ground meat, garlic powder, salt, and pepper. Hand-mix the ingredients and form them into two patties. Heat a pan to medium high heat. When hot, add cooking oil and cook the patties for three minutes on one side. Flip and cook for three minutes on the other side, or to your desired degree of doneness.  Slice open the buns. Heat a pan to low heat and add a bit of butter. Toast the bread in the pan, one side at a time, until they are lightly browned. To assemble the burger: Place watercress leaves on the bun, add the burger patty, top with a slice of cheese, and generously spread 2 tablespoons or more of Artichoke Bruschetta on top. Add mustard to taste.  Serve hot immediately.