Bring a pot of salted water to a boil. Cook the pasta 1 minute less than the packet instructions. Drain, reserving roughly ½ cup of pasta water.
Slice the steak into thin strips and place in a bowl. Season with salt and pepper to your liking.
Place a large, high-rimmed pan over high heat. Add the oil and sear the steak in batches for 2 minutes per side, or until golden (this will land around medium; sear an extra 30–60 seconds per side if you prefer it further done). Remove and set aside.
In the same pan over medium-high heat, add the butter and let it melt. Add the garlic and sauté for 1 minute. Deglaze with the stock and cook for 1 minute. Add the evaporated milk or cream, smoked paprika, chilli powder or flakes, salt, and pepper. Mix to combine, bring to a simmer, then reduce the heat to low and cook for 5–6 minutes, or until reduced.
Add the spinach and cooked pasta and cook for 1 minute, until the spinach has wilted and the pasta is coated. Add the steak and its resting juices, mix to combine, and remove from the heat.
Serve in 6 x 750ml meal prep containers. Garnish with parsley and Parmigiano Reggiano.