Set the oven to 190°C (375°F).
Follow the instructions on the wrapper of the Lasagna sheets to prepare them. Drain and set them aside.
Melt 4 tablespoons of butter in a skillet on low heat.
Chop the onion and add it to the skillet. Cook until the onion becomes tender and golden.
When the onion begins to soften, add the garlic and onion powders. Quickly blend the garlic until it becomes fragrant, and sauté it for one minute.
When adding the flour, whisk the mixture for two to three minutes, or until it is smooth.
In addition, incorporate the vegetable stock.
Mix the milk and cream one at a time which allows the sauce to thicken.
Reduce the heat while whisking.
After removing the mixture from the heat, add the broccoli, spinach, and carrots.
In a separate bowl, combine mozzarella, ricotta, romano, asiago, and parmesan cheeses by blending.
Melt the remaining butter in another bowl. Mix the melted butter with three tablespoons of the cheese mixture, along with Ritz crackers, salt, and all-purpose spice.
Spray the casserole dish with nonstick cooking spray.
Layer three noodles on the end of the dish.
Spoon one-third of the veggie mixture over the noodles.
Place half of the cheese mixture on top of the veggie mixture.
Add three more lasagna noodles, followed by another third of the combination of veggies, and the remaining half of the cheese mixture.
Cover it with the remaining veggie mixture after arranging the final three lasagna noodles on top.
Top the lasagna with salty crackers.
Cook for ½ hour.
Allow it to cool for ten to fifteen minutes before serving to avoid fracturing the pieces. Enjoy your white sauce and vegetable lasagna!