Ingredients:
1 tablespoon olive oil
1 tablespoon butter
1 leek, trimmed, thinly sliced
2 ribs celery, thinly sliced
2 carrots, peeled, finely diced
4 sprigs fresh thyme
1 tablespoon minced fresh parsley
11/2 pounds lean ground beef
1 tablespoon all-purpose flour
Salt and fresh black pepper
1 cup sliced fresh mushrooms
2 cups hot beef stock or water
14 ounces spaghetti
1 tablespoon grated lemon zest
Freshly grated Parmesan for serving

Directions:
Heat the olive oil and butter medium-hot in a pan. Cook the leek for 5 minutes. Add the carrots, celery, thyme and parsley and cook 5 minutes more.

Add the beef and cook, stirring to crumble, until browned. Sprinkle with the flour, sea salt and pepper, to taste. Stir for 1 to 2 minutes to cook the flour.

Add the mushrooms and gradually stir in the hot stock. Simmer, partly covered, 30 minutes or to desired consistency.

Meanwhile, in boiling salted water, cook the spaghetti until tender but firm. Drain well.

Toss spaghetti with meat sauce. Add the lemon zest and serve with grated Parmesan.

Makes 4 to 6 servings.