Chicken Tetrazzini (creamy chicken mushroom pasta bake)

Bahan-bahan (8 porsi)

• 500 g / 1lb spaghetti or other long pasta, cooked per packet ((penne, macaroni, ziti ok too) (Note 1))
• 2 tbsp (30g) butter
• 500 g / 1lb chicken thighs (, skinless boneless (Note 2))
• 4 tbsp (60g) butter (, unsalted)
• 500 g / 1lb mushrooms (, sliced 1/2 cm / 1/5" thick)
• 2 g arlic cloves (, minced)
• 1 onion (, finely chopped)
• 4 tbsp flour
• 2 cups milk (, any fat, any type)
• 1 cup cream (, heavy / thickened (sub more milk))
• 2 cups chicken stock/broth (, low sodium (or water + 2 stock cubes))
• 1/2 tsp black pepper
• 1 tsp salt
• 2 cups cheese (, shredded (cheddar, jack, colby - not mozz))