4 cups strained tomatoes (see note)
1 medium onion
4 tablespoons butter, cut into four roughly equal pieces
3/4 teaspoon kosher salt
3 cups whole milk
1/2 cup all-purpose flour
8 tablespoons (1/2 cup or 1 stick) butter
3/4 teaspoon kosher salt
1/2 teaspoon white (or black) pepper
A few grinds of fresh nutmeg
A combination of (you’ll need a generous 3 cups):
8 to 12 ounces Italian sausage
12 to 16 ounces white or Cremini mushrooms, sautéed (see separate recipe)
1-1/2 cups all-purpose flour
2 teaspoons olive oil
1 tablespoon butter, melted
6 ounces Parmigiano cheese, coarsely grated
1-1/2 cups shredded mozzarella, provolone or a combination
Make the tomato sauce
Cut the stem end off the onion, leaving the root end attached. Cut the onion into quarters, making sure that a portion of the root holds each quarter together. Peel the quarters and place them in a medium saucepan along with the butter and the strained tomatoes.
Bring the mixture to a low simmer (a bubble every second or so) and cook for 45 minutes, or until the fat floats to the top.
Strain out the onion, stir in the salt, and set aside.
Make the balsamella
Heat the butter over medium heat until it melts and starts to foam. As soon as the foam dies down, whisk in the flour all at once, stirring to make it smooth. Add the milk – a little at a time at first – continuing to whisk. Once all the milk is added, bring the sauce to a low simmer. Stir in the salt, pepper and nutmeg. Simmer for ten minutes, stirring often, then remove from heat. Set the sauce aside.
Prepare the sausage
If your sausage is in casings, strip the casings off, then chop the sausage roughly.
Over low heat, sauté the sausage until there’s no more pink showing. Remove the sausage from the pan with a slotted spoon and drain on paper towels.
Make the pasta
Lay out a couple of long (about 3 feet) sheets of parchment paper side by side. It helps to have a ruler and scissors handy, along with a roll of plastic wrap.
Place all the ingredients in the bowl of a food processor and process until dough is pebbly but holds together when pinched between the fingers. Dump out onto a lightly floured surface and knead a few times until the dough stays in a ball. Flatten the ball into an oval.
Feed the dough through a pasta roller set on the widest setting. Fold the dough into thirds and repeat rolling at the same setting. Fold the dough again into thirds (going the other way) and repeat. Do this five or six more times, until dough is very smooth and a little elastic. Lay the strip of dough on a lightly floured surface, cutting it in half (or quarters, if you’re doing this without a helper) and working with one piece at a time if necessary. Using plastic wrap, cover the pieces of dough you’re not working with.
Set the roller one setting thinner and feed the dough through. Continue feeding, advancing the roller setting one notch each time, until you’re at the next-to-last setting. The dough should be thin but not transparent. If dough is at all sticky at any point, sprinkle lightly with flour.
When you reach the thinnest setting, start cutting your noodles. They should be the length of your lasagna pan, and the width of your pasta roller. Lay the cut noodles on the parchment paper. Noodles should not touch each other.
Cover them with plastic wrap until you’re ready to assemble.
Heat your oven to 375°F.
Brush the bottom of your baking dish with the melted butter and spread a thin layer of balsamella over that. (Don’t worry if the balsamella isn’t even; it’s just to anchor the first layer of pasta.)
Start with a layer of noodles over the butter/balsamella in the bottom of your dish, minimizing any overlaps (not more than 1/4″). Spoon some tomato sauce (not too thickly) over the noodles. Sprinkle some sausage (again, not too much), then dot with dollops of balsamella (a small ice-cream scooper is useful here), and dust with grated Parmagiano-Reggiano.
Repeat at least five more times, pressing each layer of noodles onto the fillings below – this will even out the balsamella. Be sure to leave enough tomato sauce to spread on top of a final noodle layer.
Sprinkle the mozzarella/provolone over that last coating of tomato sauce.
Cover the casserole with aluminum foil, being careful not to let the foil rest on the cheese topping. (We usually splurge on foil here, setting the casserole onto a piece of 18”-wide heavy-duty foil, cut about 2-1/2 times as long as the dish. Bring the ends up and crimp into a tent, then seal the sides.) Place the whole arrangement on a rimmed cookie sheet (consider lining that with additional foil or parchment paper for easier clean-up).
Bake for 25 minutes, then remove the foil covering (or if using the tent method, just open it up and roll it back). Bake for another 20 minutes, or until the top is browned and bubbly.
Let the lasagna sit for about 15 minutes to allow the filling to settle. Cut into rectangular portions and serve.
Note: we like Pomi brand strained tomatoes for this and similar dishes. The quality is good with a fresh tomato taste. This brand contains no salt, though, so if you use another brand, check the salt content and adjust accordingly.