Heat the broiler. Rub jalapeno halves with oil, place skin-side up on a small rimmed pan and broil 6 inches from the heat for 5 to 7 minutes until blistered. Cover in a bowl for 5 minutes, then peel loose skin, pat dry and cut into short strips.

Mix cream cheese, garlic powder and salt until smooth. Spread a thin layer over the inner face of each bread slice.

Divide half the Jack over 2 slices, add jalapeno strips and the remaining Jack, then close with the other slices.

Butter the outside faces and cook in a large skillet over medium-low heat for 4 minutes. Turn, cover for 2 minutes, then uncover and cook for 2 to 3 minutes more until crisp and melted.

Rest for 1 minute and cut each sandwich in half before serving.