Heat a large pot under medium heat. Add olive oil, garlic and onions. Saute until fragrant, for a minute or two, avoid browning. Then add ground beef
Saute ground beef until it is no longer pink. Add carrot and celery, and saute for about one minute.
Add the liquids - peeled tomatoes and tomato paste. Stir to combine. Heat it on medium high heat and let it come to a boil.
Add the rest of the seasonings - basil, oregano, beef bouillon, salt and pepper. Stir to combine. Lower heat to medium heat and let it cook for another ~10 minutes, or until sauce thickens.
Remove from heat and set aside.
Béchamel Sauce
Add butter to a medium pot and heat under medium heat.
Once butter is melted (avoid browning butter), add flour to pot. Using a whisk, whisk to combine. Mixture will be slightly clumpy.
Immediately add milk into the pot and bring to medium high heat so that it comes to a boil. Whisk continuously until mixture is smooth and thickens.
Once mixture reaches desired thick consistency, add salt and pepper. Stir to combine, then remove from heat.
Assemble Lasagna
Pre heat oven to 375°F
Bring a thin layer of bolognese sauce to the bottom of a deep 9" x 13" dish.
Start layering with three sheets of rectangular lasagna sheets (see Note 1), then add 1/3 of the bolognese sauce, and then 1/3 of the béchamel sauce.
Repeat Steo 2 two more times. There should be a total of three sets of lasagna sheets/bolognese sauce/béchamel sauce layers.
The top layer should be béchamel sauce. Sprinkle it with mozzarella cheese to top it off.
Bring casserole dish to oven and place a cookie sheet under the casserole dish to catch any potential drippings. Bake for 45 minutes, then (optional) broil for 2 minutes to brown the top.
Remove dish from oven and let it sit for 20 minutes before cutting into lasagna.
Garnish with parsley and serve! Enjoy!
Notes
Note 1: boil lasagna sheets according to package instructions if it is not oven ready.