Preheat the oven to 350°F (175°C). Grease your baking dish generously with olive oil.

Sauté the sliced onions in a large skillet with a splash of olive oil until they turn translucent, about 5-7 minutes.

Add the sliced mushrooms and chopped kale to the skillet, seasoning with salt and pepper. Cook for another 3-4 minutes.

Whisk together the eggs, milk, Italian seasoning, and any remaining salt and pepper in a mixing bowl until fully combined.

Fold the cubed baguette and sautéed vegetable mixture into the egg blend gently to avoid falling apart.

Transfer the mixture into your greased baking dish, spreading it evenly, and top with cheddar cheese.

Bake for 35-40 minutes until set and golden brown. Let it rest for a few minutes before slicing.