For the muffins, mix pumpkin, milk, egg, Bisquick, sugar, nutmeg, cinnamon, and ginger in a bowl until just combined. Don't overmix. Fill muffin cups about 3/4 full.
For the streusel, mix Bisquick, sugar, cinnamon, and butter in a small bowl until crumbly. Sprinkle evenly on muffin cups. Bake 13-15 minutes in preheated oven. Then, enjoy the muffins!