Process flour, eggs and 1 tsp sea salt in a food processor until a dough forms, form into a disc, wrap in plastic wrap and set aside to rest (1 hour).
Meanwhile, for pea and ricotta filling, blanch peas until tender (4-5 minutes), drain and transfer to a food processor. Add parmesan, parsley and lemon rind, process to combine, season to taste and refrigerate until required.
Divide dough in half, then working with one piece at a time and covering remaining dough with a damp tea towel, pass through a pasta machine, rolling and folding and reducing settings notch by notch until 2mm thick. Cut out 8cm-diameter rounds with a pastry cutter and place in a single layer on a lightly floured tray. Working with one round at a time, place 1 tsp pea and ricotta filling in centre of rounds, lightly brush edges with water, fold over to enclose and press edges to seal, ensuring no air is trapped inside. Brush ends lightly with water, bring together, press to seal and set aside on a lightly floured tray.
Heat oil in a saucepan over medium-high heat, add onion, prosciutto and garlic and stir occasionally until tender (2-3 minutes). Add stock and peas and simmer until peas are tender (3-4 minutes). Add sage and lemon juice, pulse with a hand-held blender until coarsely puréed, season to taste and keep warm.
Cook tortellini in batches in a large saucepan of boiling salted water until just al dente (2-3 minutes), remove with a slotted spoon, add to pea mixture and toss to combine. Divide among warm serving bowls, scatter with parmesan and serve hot.
This recipe is from the October 2012 issue of Australian Gourmet Traveller.