Potato-and-Sausage Torrelli with Ragù

Bring large pot of salted water to boil.

Add potatoes and sausage; boil until sausage is cooked through, about 10 minutes.

Transfer sausage to plate. Continue to cook potatoes until tender, about 15 minutes.

Drain well. Peel warm potatoes; place in large bowl. Using hand masher, mash potatoes to smooth paste.

Mix in cheese, then next 6 ingredients. Finely chop sausage; mix in. Cover; set filling aside at room temperature up to 1 hour.

Mound flour on work surface. Make large shallow well (about 5 inches in diameter) in center.

Add eggs, oil and salt to well. Using fork, whisk eggs, oil and salt to blend. Gradually work in enough flour from around egg mixture to form soft dough in center of flour ring (there will be flour left over). Gather dough into ball. Knead dough on work surface until smooth and elastic, working in more flour if sticky, about 10 minutes. Cover dough with plastic; let rest 45 minutes (dough will become soft and malleable).

Rolling and filling pasta

Line 2 large baking sheets with smooth kitchen towels or parchment paper (use parchment if planning to freeze tortelli).

Cut dough into 4 pieces.

Turn pasta machine to widest setting. Flatten 1 dough piece into rectangle. Cover remaining pieces with plastic wrap. Run dough through machine 3 times. Fold uneven ends over to make straight edge. Run dough through machine 2 more times, dusting lightly with flour if sticky. Adjust machine to next narrower setting. Run dough through machine 3 times.

Cut dough strip in half crosswise for easier handling (strip becomes very long as it gets thinner). Working with half of dough strip and keeping other half covered with plastic to prevent drying, repeat running dough through machine 3 times on each narrower setting until pasta is 1/16 inch thick, dusting with flour very lightly if sticky (each dough strip will be about 20 inches long and 4 inches wide).

Place 1 dough strip on work surface. Starting 3/4 inch in from 1 short side, drop filling by heaping teaspoonfuls along 1 long side of strip, spacing 1 inch apart and about 1/2 inch in from edge. Fold opposite long side of dough over mounds of filling. Press around mounds of filling to release any air, then press dough between mounds to seal. Press edges together to seal.

Cut dough between mounds of filling into individual tortelli.

Transfer to prepared sheets. Make more tortelli with second dough strip.

Repeat rolling out reserved pasta dough pieces into 2 strips, then filling and shaping into tortelli until all filling is used. Reserve remaining dough for another use. (Tortelli can be made ahead. Dust lightly with flour, cover sheets with foil and refrigerate up to 4 hours or freeze up to 2 weeks. Cook without defrosting.)

Rag

Heat olive oil in heavy large pot over medium-high heat.

Add sausage and saut until no longer pink, breaking into small pieces with back of fork, about 2 minutes.

Add chopped celery, carrot, onion, parsley, garlic and dried crushed red pepper. saut until vegetables begin to soften, about 5 minutes.

Add chicken stock and tomato paste. Reduce heat to medium-low and simmer until rag thickens slightly and is reduced to 3 cups, stirring occasionally, about 20 minutes. Season rag to taste with salt and pepper. (Can be prepared 1 day ahead. Cool slightly. Refrigerate uncovered until cold, then cover and keep refrigerated.)

Serving

Cook tortelli in large pot of boiling salted water until just tender, about 5 minutes (or 6 minutes if frozen). Using large sieve or strainer, transfer tortelli to colander set in bowl. Empty water from pot.

Add butter to same pot; melt over medium-high heat.

Add tortelli; toss gently until warm and coated with butter. Meanwhile, bring rag to simmer. Divide tortelli among plates.

Drizzle with butter from pot. Top with rag; sprinkle with cheese.

Garnish with parsley.

Serve with more cheese and any remaining rag.