Meanwhile, heat a large saucepan over medium heat. Once hot, add olive oil and garlic, stirring quickly to ensure it doesn’t burn.
Next, reduce heat slightly and add flour (starting with lower end of range // 2 Tbsp as original recipe is written) and whisk to combine. Cook for about a minute and then add veggie stock and milk and use a flat spatula to mash the flour into the liquid.
Add salt, pepper, pesto, grated parmesan cheese and stir. Cook on medium heat until it bubbles, and then reduce heat to low-medium heat and cook until thickened. Taste and adjust seasonings as needed – I usually add a bit more salt and pepper toward the end.
If you notice the sauce is too thick, add a little more milk or broth. If too thin, add a little more flour and whisk to combine. Alternatively, you can thicken with more parmesan cheese.
Once sauce is ready, add the peas and stir. Then add the drained cooked pasta and toss to combine, adding more salt and pepper if needed. Serve immediately with additional parmesan cheese on top. Garlic bread and steamed broccoli or peas are excellent additions to this simple dish.