In large skillet, cook sausage and onion over medium heat until sausage is no longer pink; drain. Stir in cream cheese, Monterey Jack cheese and marjoram; set aside.
In mixing bowl, combine flour and salt. Add milk, eggs and oil; mix well. Heat lightly greased 8-inch nonstick skillet; pour 2 tablespoons batter into center of skillet. Lift and tilt pan to evenly coat bottom. Cook until top appears dry; turn and cook 15 to 20 seconds. Remove to wire rack.
Repeat with remaining batter, adding oil to skillet as needed. When cool, stack crepes with waxed paper or paper towels in between.
Spoon 2 tablespoons of sausage mixture onto center of each crepe. Top with two asparagus spears. Roll up; place in two greased 13-in. x 9-in. x 2-in. baking dishes. Cover and bake at 375° 15 minutes. Combine butter and sour cream; spoon over crepes. Bake 5 minutes longer or until heated through.