Cook the potatoes in a large saucepan of salted boiling water for 5 minutes, then add the pasta and cook according to the packet instructions until al dente. When there are 5 minutes of the cooking time remaining, add the cabbage.
Meanwhile, heat the oil in a small saucepan over a low heat. Add the garlic and, as it starts to colour, tip in the mascarpone and Gorgonzola, stirring until melted. Remove from the heat.
Just before draining the pasta, stir a ladleful of the cooking water into the cheese sauce. Drain the pasta and transfer to a large serving bowl. Pour in the cheese sauce, toss well to combine and serve immediately with a scattering of grated Parmesan.