Keto Veg and Egg Casserole
⏲ ~52 min total · prep 15 · cook 37 · 4 servings
Dinner⏱ 42 min total🔥 3.0g net carbs⚡ ≈489 kcal/serving~9% of calories from carbs
By the KFI Test Kitchen · Tested & approved by Jason Lieu, KFI recipe editor
Published Sep 15, 2026 · Updated Sep 15, 2026
Ingredients
- 8 large eggs
- 1/2 cup heavy cream
- 1 tsp Dijon mustard
- 1 tbsp butter
- 8 oz mushrooms, sliced
- 2 cups small broccoli florets, chopped bite-size
- 1 red bell pepper, diced
- 1 1/2 cups shredded cheddar, divided
- 1 tsp kosher salt, divided
- 1/2 tsp black pepper
- 2 tbsp fresh chives, chopped
Instructions
- Heat the oven to 350°F and butter an 8x8-inch baking dish.
- Melt the butter in a 10-inch skillet over medium-high and cook the mushrooms 4-5 minutes, until they release their water and it fully evaporates and they begin to brown — this step keeps the casserole from going watery.
- Add the broccoli and bell pepper and cook 3 minutes, until crisp-tender; season with 1/2 teaspoon of the salt and spread the vegetables in the prepared dish.
- Whisk the eggs, cream, Dijon, remaining 1/2 teaspoon salt, and pepper about 1 minute, until completely uniform and lightly frothy, then stir in 1 cup of the cheddar.
- Pour the custard over the vegetables, nudge the dish so it settles evenly, and scatter the remaining 1/2 cup cheddar on top.
- Bake 30-35 minutes, until the center is puffed, barely jiggles like set gelatin, and a knife inserted in the middle comes out clean.
- Rest 10 minutes — it will slump slightly and then slice into clean squares — and top with the chives before serving.
Why this recipe works
- Mushrooms dry-cooked first The mushrooms cook until their water releases and evaporates completely, 4 to 5 minutes. Mushrooms raw into the custard leak it all back in the oven, leaving the casserole in a puddle.
- Dijon in the custard A teaspoon of Dijon disappears into the eggs and cream and comes out as depth rather than mustard flavor. It is the difference between a flat custard and one with a spine.
- The 10 minute rest Out of the oven it jiggles; after 10 minutes it slumps slightly and slices into clean squares. Cutting early gives you spoons, not slices.
Tips for making this recipe well
Read the center, not the clock
Done looks like a puffed center that barely jiggles, like set gelatin. A knife in the middle should come out clean. Ovens vary, so start checking at 30 minutes.
Chop the broccoli small
Small florets turn crisp-tender in their 3 minutes of skillet time and finish in the bake. Big chunks stay raw-stemmed and squeaky.
Whisk the custard a full minute
Uniform, lightly frothy custard bakes evenly. A lazy stir leaves streaks of white and yolk and an uneven set.
Settle the dish
A gentle nudge after pouring settles the custard into the vegetables. Trapped pockets bake as holes.
Divide the cheddar
One cup goes into the custard, half a cup on top for the browned lid. Adding it all to the top flattens the flavor of the middle.
Serving suggestions
Three point zero net carbs a serving is the number that makes this a weekly repeat, and forty-two minutes is why it lives on weekends. Cut into squares, it covers breakfasts for days without a single morning of cooking. Serve wedges hot from the dish with chives scattered over and hot sauce on the table; sliced avocado next to it rounds the plate out. The casserole also travels: a covered square holds together in foil for a potluck table better than any scramble would.
Storage and meal prep
Cover leftover squares in the fridge for 3 to 4 days; they reheat in the microwave in about a minute or in a 350°F oven until hot through. The dish freezes well baked: cool it completely, wrap squares individually, then keep them up to 2 months. Thaw overnight in the fridge before reheating. Egg casseroles are fully cooked at a 165°F center, so a thermometer removes all doubt on both the first bake and the rewarm.
Variations worth trying
- Sausage version Brown 8 ounces of breakfast sausage with the mushrooms and drain the fat. It turns a side-dish casserole into a main.
- Pepper jack lid Swap the top layer of cheddar for pepper jack. The middle stays mild while the top carries a slow burn.
- Spinach instead of broccoli Wilt 5 ounces of spinach with the mushrooms and squeeze out the water first. Wet spinach is the same problem as wet mushrooms, only faster.
- Make-ahead assembly Cook the vegetables and mix the custard the night before, then cover and refrigerate the assembled dish. Bake straight from the fridge with about 5 extra minutes and the usual center test.
Frequently asked questions
Can I assemble it the night before?
Yes. Cook the vegetables, mix the custard, then refrigerate the assembled dish covered overnight. Bake straight from the fridge with about 5 extra minutes and the usual center test.
Why did mine turn out watery?
Almost always the mushrooms: their released water never evaporated before baking. Cook them until the pan goes dry and they start to brown.
How do I know it is done?
The center should be puffed, barely jiggling like set gelatin, with a clean knife in the middle. A thermometer reading 165°F at the center settles any argument.
Can I freeze the whole dish?
Baked squares freeze better than an unbaked dish, up to 2 months wrapped well. Cool completely first, then thaw overnight in the fridge and reheat covered.
Does it work without the cream?
The half cup of heavy cream is what makes the set tender rather than rubbery. Whole milk works in a pinch, but expect a firmer, less rich slice.
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