1. Cook pasta as package directs in a large pot of salted boiling water.
2. Meanwhile, set aside 3/4 cup loosely packed small mint leaves. Put remaining mint and 3/4 tsp. salt, the nuts, garlic, parmesan, pepper, and oil in a food processor. Pulse just until coarsely puréed.
3. Transfer pesto to a large bowl and stir in gorgonzola and mascarpone.
4. Drain pasta, saving 1 cup pasta water, then transfer to bowl with pesto. Toss to coat well. Quickly toss with reserved mint leaves and add a little pasta water if needed for a looser texture. Serve immediately and season with salt to taste.