For the pesto: In a food processor, combine the walnuts, garlic, jalapeno, cheese, salt and pepper. Process until the mixture is smooth. Add the spinach and arugula and process until blended. With the machine running, gradually add the olive oil.
Bring a large pot of salted water to a 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 1 cup 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.
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.