Fried steak with creamy spinach

Ingredients:

• 0.7 kg flank steak from the belly part
• Olive oil to brush the steak
• 1.5 tbsp unsalted butter
• Half an onion, finely chopped
• 1.5 tbsp flour
• 1.5 cups whole milk
• 2 x 280g packages frozen chopped spinach, thawed and squeezed out
• 3/4 tbsp. grated parmesan
• 0.5 tsp. grated lemon zest
• 1/4 teaspoon freshly grated nutmeg

Preparation:

1. Heat a grill pan over medium-high heat. Pat the steak dry and lightly brush with olive oil. Season with 1.5 teaspoons of salt and 2-3 teaspoons of black pepper. Grill, turning once, for 10-13 minutes for medium-rare. Transfer the steak to a cutting board to rest for about 10 minutes.
2. Meanwhile, melt the butter in a medium saucepan over medium heat. Add the onion and cook until softened, about 5 minutes. Add the flour and cook, stirring, for 1 minute. Remove from heat and gradually whisk in the milk. Return to medium heat and simmer, stirring, until the sauce thickens slightly, about 2 minutes.
3. Add the spinach, 1/4 cup water, 1/2 cup Parmesan, lemon zest, and nutmeg and cook, stirring occasionally, until the sauce thickens and the spinach is wilted, about 10 minutes. Thin with more water if needed. Stir in the remaining 1/4 cup Parmesan and season with salt to taste.
4. Slice the steak thinly against the grain and serve with spinach.