Chef John's Lasagna

Make the sauce: Cook and stir ground beef and sausage in a large saucepan over medium heat until browned and crumbly, about 10 minutes. Stir in mushrooms, salt, black pepper, Italian seasoning, and pepper flakes. Increase the heat to medium-high and cook until mushrooms have given off their juices and the bottom of the pan is almost dry, 4 to 6 minutes.

Pour marinara sauce into meat mixture. (If using jarred sauce, add a little water to each jar and shake to get all sauce out of the jar; add to meat mixture.) Reduce the heat to low and simmer until meat is extremely tender, about 2 hours; add more water if sauce becomes too thick. Skim fat, then season sauce with salt and black pepper. Turn off the heat.

When the sauce is almost finished, make the pasta: Bring a large pot of salted water to a boil. Cook lasagna in the boiling water, stirring occasionally, until cooked through but firm to the bite, about 8 minutes. Drain and rinse lasagna noodles; set aside in a bowl of cold water.