For lobster oil, preheat oven to 180C. Halve lobster lengthways using a sharp knife, remove tail meat, coarsely chop and refrigerate until required. Place shell on an oven tray and roast until dry and brittle (40-45 minutes). Heat 1 tbsp grapeseed oil in a saucepan over medium-high heat, add carrot, onion, celery and garlic and sauté until soft (4-5 minutes). Stir in tomato paste and cook until aromatic (1-2 minutes). Add shell and break up with a wooden spoon, then add peppercorns, bay leaf and 400ml water and bring to a simmer. Add remaining oil and simmer over low heat until flavoured (1-1½ hours). Skim scum from surface with ladle (discard), then ladle off oil and refrigerate until required. Discard solids and water. Makes about 300ml. Oil will keep refrigerated in a sterilised jar for 3 weeks.
For tagliolini, combine flour and semolina in a large bowl, make a well in centre, add yolks, oil and enough water to bring dough together (about 1 tbsp), gently combine and knead on a lightly floured work surface until smooth and elastic (8-10 minutes). Wrap in plastic wrap and set aside for 10 minutes. Feed pasta through rollers of a pasta machine set on its widest setting, rolling and folding until dough is smooth, and reducing settings notch by notch until pasta is 2mm thick (dust with extra flour if dough gets too sticky). Cut pasta into 30cm lengths, then cut each sheet into 5mm-wide strips. Bring a large saucepan of salted water to the boil over high heat, add pasta, stir and cook until al dente (1-2 minutes). Drain and keep warm.
Heat 125ml lobster oil in a large frying pan, add half lobster meat and sauté until just cooked (1-2 minutes), add half warmed pasta and herbs, toss to combine with tongs, transfer to serving bowls, repeat with remaining ingredients and serve immediately.