This Keto Broccoli and Cauliflower Au Gratin with Sausage is one of those weeknight solutions that feels indulgent but keeps you firmly on track with low-carb goals. I first pulled this together on an evening when I wanted something cheesy and satisfying without reaching for potatoes or pasta. The result immediately became a family favorite: the vegetables stay tender-crisp, the sauce is luxuriously creamy, and the smoky sausage adds just the right amount of savory depth. Every bite has contrasting textures—soft florets enveloped in a velvety cheddar blanket and pockets of caramelized sausage that give the dish a hearty backbone.

I discovered the balance between cream cheese and heavy cream in this version while experimenting with ways to thicken a sauce without flour. The combo creates a silky mouthfeel that clings to the vegetables and browns beautifully under a short bake. We usually serve this at casual dinners and holiday sides alike; it’s one of those dishes that prompts people to ask for the recipe immediately. It reheats well, freezes fine for single portions, and adapts easily to what’s in your fridge—making it a practical yet comforting option any time of year.

Ingredients

• Cauliflower florets (3 cups): Look for tight, white heads with firm stems; cut into bite-sized florets. Light steaming softens them slightly so they finish perfectly in the oven without becoming mushy.
• Broccoli florets (2 cups): Younger, brighter crowns yield a sweeter flavor. Trim thick stems so the florets cook evenly when briefly steamed.
• Sliced smoked sausage (12 ounces): I use smoked kielbasa or a hardwood-smoked link; the smoke adds a deep savory note. Choose a higher-fat variety for the best texture and flavor.
• Butter (2 tablespoons): Unsalted butter for the roux base; adds richness and helps soften the onion.
• Onion (1/2, diced): A small yellow onion gives sweetness and depth when sautéed until translucent.
• Minced garlic (2 teaspoons): Fresh is best—adds fragrance and a punch that complements the cream and cheese.
• Cream cheese (2 ounces, softened): Full-fat, at room temperature so it melts smoothly into the sauce and creates a velvety texture.
• Heavy whipping cream (2/3 cup): This is the primary thinning agent for the sauce; it creates richness and helps the shredded cheddar melt smoothly.
• Shredded cheddar cheese (1 1/2 cups): Sharp cheddar offers the best balance of flavor and meltiness. Pre-shredded is convenient but freshly shredded melts cleaner.
• Salt and black pepper: To taste—season progressively as you build the sauce so the final dish is balanced.

Instructions

Preheat the oven: Set your oven to 350°F and position a rack in the center so the dish browns evenly during the short bake. Preheating ensures the casserole sets quickly and the cheese melts consistently. Sear the sausage: Heat a skillet over medium-high heat. Add the sliced smoked sausage in a single layer and sauté until the edges are nicely seared and a little caramelized, about 4–6 minutes. Transfer to a plate and set aside—searing concentrates flavor and releases some fat to carry taste into the sauce. Sauté the aromatics: In a medium pot over medium heat, melt the butter. Add the diced onion and cook until softened and translucent, about 4–5 minutes. Stir frequently to prevent browning—gentle sweetness is what we want, not crisped bits. Add garlic and cream cheese: Stir in the minced garlic and cook 30 seconds until fragrant. Add the softened cream cheese and stir until it completely melts into the butter and onions. Lower the heat if it threatens to stick—slow melting prevents separation. Finish the sauce: Pour in the heavy whipping cream and whisk until smooth. Simmer over medium-low, stirring frequently, until the mixture thickens slightly, about 3–5 minutes. Remove from heat and stir in the shredded cheddar until it melts into a glossy, cohesive sauce. Taste and season with salt and pepper. Combine and bake: In a large mixing bowl, combine the lightly steamed cauliflower and broccoli with the seared sausage. Pour the cheese sauce over the bowl and gently toss to coat everything evenly. Transfer to a greased 9x9 baking dish and spread into an even layer. Bake for 15–20 minutes until bubbly and just starting to brown on top.

Storage Tips

Store cooled portions in airtight containers in the refrigerator for up to 4 days. For longer storage, portion into freezer-safe containers and freeze for up to 3 months—label with the date. When reheating from frozen, thaw overnight in the refrigerator and reheat in a 350°F oven covered with foil for 20–30 minutes until warmed through; remove foil for the last 5–10 minutes to refresh the top. Avoid prolonged high heat in the microwave to prevent the sauce from breaking; adding a splash of cream before reheating helps revive cream-based sauces.

Ingredient Substitutions

Swap smoked kielbasa for Italian sausage (mild or hot) for a flavor shift—note that raw sausage should be fully cooked first. Use Gruyère or fontina in place of cheddar for a nuttier, more meltable sauce; reduce salt slightly if using aged cheeses. For dairy-free options, replace heavy cream with full-fat coconut milk and cream cheese with a firm, dairy-free spread—results will be slightly coconut-forward. To make it vegetarian, omit the sausage and add roasted mushrooms or smoked tempeh for umami and texture.

Serving Suggestions

Serve this gratin straight from the oven with a handful of fresh parsley or chives sprinkled on top for color and brightness. Pair with a crisp green salad dressed in a lemon vinaigrette to cut the richness, or offer roasted Brussels sprouts and a vinegar-based slaw. For holiday tables, place small ramekins for individual servings; for casual dinners, serve family-style with crusty keto bread or roasted radishes on the side.

Cultural Background

Gratins have French roots—traditionally a creamy, browned topping over vegetables or potatoes. This low-carb version adapts that classic technique by replacing starchy potatoes with cruciferous vegetables and using high-fat dairy to achieve a similar mouthfeel. The addition of smoked sausage nods to Central and Eastern European flavors where sausage and cabbage or root vegetables are often combined in hearty, comforting preparations.

Seasonal Adaptations

In spring, add fresh asparagus tips or peas for color and sweetness; in autumn, swap broccoli for roasted butternut squash if you’re not strictly low-carb. Holiday versions can include sage and a pinch of nutmeg in the sauce for warmth. For summer barbecues, fold in grilled zucchini and use a smoked cheddar to enhance outdoor flavors. Small tweaks keep the dish feeling fresh across the year.

Meal Prep Tips

To meal-prep, steam and cool the florets and pre-cook the sausage at the start of the week. Make the cheese sauce and refrigerate it separately in an airtight jar; assemble and bake within 24–48 hours. Portion into individual containers and reheat for lunches—this reheats beautifully when you add a splash of cream and warm in the oven for 10–15 minutes, finishing under the broiler for 1–2 minutes for a golden top.

Bring this dish to your next casual dinner or tuck it into your weekly rotation for satisfying, low-carb meals. It’s approachable, adaptable, and reliably comforting—give it a try and make it your own with the seasonings and proteins you love.