Cut the crust off the bread slice and soak in the milk. Once it is soaked, add both the soaked break and the milk into the blender.
To the blender, add the walnuts, parmesan cheese, ricotta, oregano, salt, garlic, and olive oil.
Pulse to start the blending and incorporate all ingredients. Then blend until smooth. If it gets stopped up, stir with a spoon or spatula. If it really can't get going, add a tablespoon at a time of lukewarm water until it starts to blend smooth. The sauce should be very thick at this stage.
At this point, you can cook move on to warm the sauce and mix with the pasta and spinach or store in the fridge for up to a week.
Cook the Pasta according to package instructions. Drain the Pasta, but save the pasta water for thinning out the walnut sauce.
Coat the bottom of a large preheated skillet with a drizzle of Olive Oil. Then add the Walnut Sauce to heat through. (Note, the sauce will be super thick, so you may need to thin it out with pasta water. It also may more sauce than you need so you can save some of it and add it if needed). Turn the heat down to low.
Add the Baby Spinach to the sauce and mix to combine. You don't need to cook it long, just 1-2 minutes, as you want the bright green color and fresh flavor to remain. The heat of the sauce will wilt down the spinach.
Once the sauce is heated through and the spinach starts to wilt, drain the pasta and add it to the sauce. Add 2 tbls of the pasta water to thin out the sauce slightly and mix through with this pasta. Add another tbls of pasta water if needed. Finally, taste for seasoning and add salt and pepper as needed.
Serve the pasta with walnut sauce with freshly grated parmesan cheese and Enjoy!