1. 1. Preheat the oven to 350°F (175°C).

2. 2. Cook the noodles according to package instructions until al dente. Drain and set aside.

3. 3. In a saucepan, melt butter over medium heat. Stir in the flour to make a roux, then slowly whisk in the milk until smooth and thickened.

4. 4. Add the feta cheese to the saucepan and stir until melted and well combined.

5. 5. In a baking dish, layer half of the cooked noodles, followed by half of the cheddar cheese. Pour half of the feta cheese sauce over the layers. Repeat with the remaining noodles, cheddar cheese, and sauce.

6. 6. Bake in the preheated oven for 20-25 minutes, or until bubbly and golden brown on top.

7. 7. Let it cool slightly before serving.