Cook the pasta in a large saucepan of salted boiling water according to the packet instructions until al dente.
Meanwhile, melt the butter in a heavy-based saucepan over a very low heat. Add the Gorgonzola and heat, stirring, for 2–3 minutes until the cheese has melted.
Add the cream, vermouth and cornflour and whisk well to combine. Stir in the sage. Cook, whisking constantly, until the sauce boils and thickens. Season with salt and pepper and remove from the heat.
Drain the pasta thoroughly and toss with a little butter. Reheat the sauce gently, whisking well. Pour over the pasta and toss well to combine. Serve immediately, garnished with sage leaves.