Cook pasta according to package directions until "al dente," saving 1 cup of the cooking water to use later.
While pasta is cooking, place olive oil, butter, garlic, and onion in a sauce pan and saute over low heat until onion is transparent.
Return pasta to dry pan off heat. In a blender, mix ricotta cheese, eggs, and milk. Blend on low until smooth. Add the cheese mixture to the pasta, add the olive oil mixture, and add the asiago cheese and toss well until pasta is completely covered with sauce. Add reserved pasta water as needed to thin the sauce to desired consistency.
Warm entire mixture thoroughly before plating and serving immediately. Makes 6 servings. Enjoy!