1) For the pesto, combine the walnuts, garlic, jalapeno, cheese, salt and pepper in a food processor. Process until the mixture is smooth. Add the spinach and rocket and process until blended. With the machine running, gradually add the olive oil.
2) Bring a large pot of salted water to the boil over high heat. Add the pasta and cook until tender but still firm to the bite, stirring occasionally, about 8 to 10 minutes. Drain and reserve about 225ml of the pasta water. Place the cooked pasta and pesto in a large serving bowl. Toss well and thin out the sauce with a little pasta water, if needed.
3) Season with salt and pepper, to taste. Garnish with Asiago cheese shavings and serve.
*Cook's Note: For a milder pesto, remove the seeds from the jalapeno pepper.