Thinly slice the cabbage with a sharp knife or mandoline. Combine 1 tbs white vinegar, 1 tsp sugar in a large bowl. Add the cabbage and using your hands, massage for 1 min or until slightly softened. Set aside to pickle, tossing occasionally, until needed. Bring a medium saucepan of salted water to the boil for the spaghetti.
Step 2 — Prep ingredients
Wipe the mushrooms clean, then thinly slice. Thinly slice the onion. Crush or finely chop the garlic. Strip half the thyme leaves*, discarding the tough stems. Finely chop the parsley leaves, discarding the stems. Slice the chicken into strips. Crumble 1 stock cube* into a heatproof jug, add 250ml (1 cup) boiling water and stir to dissolve.
Step 3 — Brown chicken
Heat 2 tsp olive oil in a medium deep frypan over high heat. Add the chicken, season with salt and pepper and cook, stirring regularly, for 3-4 mins until golden and cooked through. Remove from the pan and reserve the pan.
Step 4 — Cook spaghetti
Meanwhile, add three-quarters of the spaghetti* to the pan of boiling water (if you're tempted to throw in all the spaghetti, just note the dish won't be as saucy). Cook, stirring occasionally, for 12 mins or until al dente. Drain.
Step 5 — Cook stroganoff sauce
Heat 2 tsp olive oil in the reserved pan over medium-high heat. Cook the mushrooms, garlic, onion and thyme, stirring, for 3-4 mins until softened. Add 1 tbs flour and cook, stirring, for 30 secs until foaming. Gradually add the stock, worcestershire sauce, three-quarters of the cream* and 2 tsp dijon mustard to the mushroom mixture and bring to the boil.
Step 6 — Get ready to serve
Reduce the heat to medium. Cook the stroganoff sauce, stirring occasionally, for 4-5 mins until slightly thickened. Taste, then season with salt and pepper. Add the spaghetti, chicken and resting juices and cook, tossing, for 1 min or until heated through. Divide the stroganoff among bowls. Scatter with the parsley and serve with pickled red cabbage.