Cook the tagliatelle in boiling salted water until al dente.
Cut half of the sage leaves into small strips.
In the meantime, let the butter heat up in a pan and slowly melt the diced Gorgonzola over a moderate heat. Add the sage leaves, whole and cut. Now gradually pour in the sweet cream, keep stirring and let the sauce thicken a little. Season to taste with pepper from the mill. If necessary, stir in a few more tablespoons of pasta water.
Drain the pasta, drain well and add to the pan with the sage / gorgonzola sauce. Mix well and serve.