Place potatoes on a baking sheet and bake at 400 degrees F for 30 minutes or until tender. Cool until you're able to handle them (I place mine in the fridge to speed this up!).
Slice potatoes lengthwise and scoop out the flesh with a teaspoon, being careful to leave enough of the sides intact so that they are sturdy enough to fill.
Mash potato flesh with a fork. Add milk, salt and garlic powder and mash until smooth.
Stir in broccoli and ½ cup cheddar. Spoon into potato shells and press down gently to fill.
Sprinkle with remaining ¼ cup cheese and bake at 400 degrees F for 10 minutes, until heated through and cheese has started to brown. Serve immediately.