Bring a large saucepan with about 2 inches of water to a boil. Add asparagus and cook until just tender, 1-2 minutes. Drain and put asparagus in a bowl of ice water to stop cooking. Drain asparagus and chop into 1/2-inch pieces.
Melt butter in a small pan over medium heat. Add leeks and cook, stirring occasionally for about 5 minutes. Add garlic and cook 1 more minute. Let cool.
Combine all ingredients in a medium bowl. Season to taste with salt.
Transfer to a greased 1-quart baking dish.
Bake for 25-30 minutes of until lightly browned on top.