For the dish
Heat a saucepan (large enough to also contain the pasta) on high heat, add the olive oil and sauté the chicken after salting it well. When it gets a golden colour add half the butter and continue sautéing for about 2 minutes and remove the chicken.
In the same saucepan, add the milk, and the béchamel sauce and stir well until it is homogenized.
Add the cheese, the pasta, the chicken, the scallions, the remaining butter and mix well. Taste and salt again if necessary.
Put the pasta mixture on a buttered baking tray and flatten it into an even layer. Place the cherry tomatoes and sprinkle with the remaining kefalotyri cheese.
Bake in preheated oven at 180oC until the surface gets a crispy crust, about 20 minutes.