Step 1Cook pasta in a large saucepan of boiling water, following packet directions, or until al dente. Add the broccolini to the pan for the last 2 minutes of cooking. Drain, reserving ½ cup of cooking water. Rinse under cold water. Drain.
Step 2Meanwhile, heat oil in a large, deep non-stick frying pan over a medium-high heat. Cook the mushrooms, stirring, for 5 minutes, or until golden and tender. Add garlic and mustard. Cook, stirring, for 1 minute, or until tender.
Step 3Add cream and ½ cup of pasta cooking. Bring to the boil, then reduce heat and simmer, stirring occasionally, until thickened slightly. Add spinach and chicken. Cook, stirring, for 2 minutes.
Step 4Add the pasta and broccolini; toss to coat. Season with cracked black pepper. Divide among four serving bowls and scatter with pine nuts, to serve.