Measure out all ingredients by weight for accurate portions. Pick spinach leaves and discard any tough stems.
Blanch spinach leaves briefly in boiling water, then drain well and transfer to a blender
Add milk to the blender and blend into a smooth, bright green spinach puree
Cook pasta in boiling salted water until al dente, then drain and set aside.
Heat butter in a pan over low heat. Add minced garlic and sauté gently until fragrant — take care not to burn it, as burnt garlic will turn the sauce bitter.
Pour the spinach puree into the pan and stir to combine with the garlic butter. Simmer briefly to thicken slightly.
Add the cooked pasta to the pan, toss well to coat every strand evenly with the green sauce
Finish with a light pinch of salt, ground black pepper and a sprinkle of dried oregano. Toss once more and serve immediately.