Some popular starches that pair well with trout include creamy mashed potatoes, roasted red potatoes, wild rice pilaf, couscous, and quinoa.  For a lighter side dish of starch, consider serving the trout alongside a fresh green salad or steamed vegetables.  To add more flavor to your starch dishes, try adding herbs like rosemary, thyme, and parsley. Additionally, you could top your mashed potatoes with butter or chives to add a little extra flavor.