Fill a large pot with water and add a few pinches of salt. Place the pot over high heat and bring the water to a boil. Add the spaghetti and cook according to package directions. Drain the spaghetti into a colander and rinse with cold water. Set aside.
While the spaghetti is cooking, prepare the vegetables. Trim off the ends of the zucchini and make zucchini noodles using a spiralizer or cut into ribbons with a peeler. Set the zucchini noodles aside. Peel the carrots and slice into ⅛-inch thick coins.
Heat ½ tablespoon of olive oil in a large sauté pan over medium-high heat. Add the zucchini noodles to the pan and cook for 1 to 2 minutes, until the zucchini noodles start to soften. Stir in a pinch of salt and plate the zucchini noodles. Add another ½ tablespoon of olive oil into the pan. Add the carrot coins and cook them for about 3 to 4 minutes. Plate the carrots and quickly wipe down the pan with a wet paper towel or a tea towel.
Add the remaining 1 ½ tablespoons of olive oil into the pan and reduce the heat to medium. Add the onions and cook them for about 2 to 3 minutes, until they start to soften. Add the minced garlic and frozen peas and stir for another minute. Add the half and half, thyme, green onions and a pinch of salt.
In a small bowl, mix the flour and water together. When the half and half starts to simmer, add the flour and water mixture. Continue cooking the sauce until it thickens and bubbles in the middle of the pan, about 2 to 3 more minutes. Turn off the heat and adjust the seasonings to your taste by adding more salt, thyme or some black pepper. Add the cooked spaghetti, zucchini noodles, and carrots into the pot and mix everything together. Serve immediately.
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