Preheat oven to 375 degrees F. Coat a 7-by-11-inch (2-quart) glass baking dish with cooking spray.Advertisement
Place chicken in a medium skillet or saucepan and add water to cover. Bring to a simmer over high heat. Cover, reduce heat to low and simmer gently until the chicken is cooked through and no longer pink in the center, 10 to 12 minutes. Drain and slice into bite-size pieces.
Heat oil in a large nonstick skillet over medium-high heat. Add leek and salt and cook, stirring often, until softened but not browned, 3 to 4 minutes. Add flour; stir to coat. Add broth, milk, sherry, thyme and pepper and bring to a simmer, stirring constantly. Add broccoli; return to a simmer. Remove from heat and stir in 1/2 cup Parmesan, mayonnaise and mustard.
Spread half the broccoli mixture in the prepared baking dish. Top with the chicken, then the remaining broccoli mixture. Sprinkle evenly with the remaining 1/2 cup Parmesan. Bake until bubbling, 20 to 25 minutes. Let cool for 10 minutes before serving.
Tips: To clean leeks, trim and discard green tops and white roots. Split leeks lengthwise and place in plenty of water. Swish the leeks in the water to release any sand or soil. Drain. Repeat until no grit remains.
Sherry is a type of fortified wine originally from southern Spain. Don't use the “cooking sherry” sold in many supermarkets--it can be surprisingly high in sodium. Instead, purchase dry sherry that's sold with other fortified wines in your wine or liquor store.
Ingredient Note: Most supermarkets sell broccoli crowns, which are the tops of the bunches, with the stalks cut off. Although crowns are more expensive than entire bunches, they are convenient and there is considerably less waste.
1/2 starch, 3 vegetable, 3 lean meat