Season chicken with 1 teaspoon salt and 1/2 teaspoon pepper. Melt 1 tablespoon butter in a large cast iron skillet over medium high heat. Working in batches, add chicken to the skillet in a single layer and cook until golden brown, about 4-5 minutes; set aside.
Melt remaining 4 tablespoons butter. Add onion and celery, and cook, stirring occasionally, until tender, about 3-4 minutes. Stir in garlic until fragrant, about 1 minute.
Whisk in flour until lightly browned, about 1 minute.
Stir in wine, scraping any browned bits from the bottom of the skillet.
Stir in chicken stock, heavy cream and Dijon; season with salt and pepper, to taste. Bring to a boil; reduce heat and simmer, stirring often, until reduced and slightly thickened, about 3 minutes.
Remove from heat; stir in cheeses until melted.
Stir in broccoli and chicken until well combined. Sprinkle with topping.
Place into oven and bake until golden brown and bubbling, about 30-35 minutes. Let cool 10-15 minutes.
Serve, garnished with parsley, if desired.
for the topping
In a small bowl, combine crackers and butter.
Notes
Use white or dark meat. Chicken breast, tenders and thighs will all work well here.
Shorten prep time. Use leftover rotisserie chicken (skipping step 1 and 2) or substitute frozen broccoli to cut down on prep time even more.
Choose a wine you will drink. A dry white wine (pinot grigio or sauvignon blanc) is great here – it does not have to be anything fancy or overpriced. Just something you don’t mind sipping on since you will have an open bottle.
Use good-quality stock. The better quality your stock, the better your casserole. Many brands love to pack in the salt so always opt for unsalted or a lower-sodium variety. Homemade stock is even better.
Freshly grated cheese goes a long way. Although pre-shredded cheese can save a few minutes in the kitchen, pre-shredded cheese contains anti-caking agents to prevent clumping – this can hinder its ability to melt properly. Freshly grated cheese will not only have a better flavor profile, but it will also melt more smoothly and evenly, yielding a far more superior chicken divan.
Top with buttery round crackers. Some recipes call for potato chips or breadcrumbs, but crushed crackers (we love Ritz) tossed with melted butter is a long-time tradition, resulting in that favorited crispy, buttery goodness.
Mix it up. Swap out the broccoli for different vegetables such as cauliflower, zucchini, carrots and peas.
Use a cast iron skillet. For the best texture and flavor, use a large, heavy-bottomed skillet that holds heat evenly. Added bonus: a cast iron skillet is oven-safe, and can go directly from the stovetop to the oven.
Serve with crusty bread. Serve with all the homemade crusty bread for dipping, sopping and dunking!
Freeze before baking. This will help preserve the texture and prevent sogginess. Always use a freezer-safe baking dish, label, date and freeze up to 2 months.