Mashed Potato Casserole

I saw a chef in AFC channel did a dish similar like this long ago. I'm not really remember the ingredients and the steps, but one thing for sure he piped the mashed potato on top of the dish before send to bake. Thus i search from internet, and I believe the most suitable title for this would be mashed potato casserole even I'm not using the said cookware.
Creativity is necessary in the kitchen, agree?

Ingredients

Mashed Potato

• potato    马铃薯
• butter    牛油
• milk    牛奶
• oregano    牛至
• a pinch of salt & pepper    少许鹽和胡椒

Filling

• cabbage    包菜
• corn kernel    玉米粒
• bacon    熏肉
• minced meat    绞肉 
• button mushroom    蘑菇   
• salt & pepper    盐和胡椒
• cheese    芝士

Steps 

Mashed Potato

1. Peel off the potato skin and cut into cubes. Steam to soft and tender.    马铃薯去皮切块，蒸软。
2. Add the butter, milk, oregano, salt and pepper. Mash to smooth puree, then fill in the piping bag.    马铃薯加进牛油、奶、牛至、盐和胡椒压成细绵的薯泥；再倒入裱花袋

Filling

1. Cook all the ingredient (except cheese) to half-cooked, seasoning with salt and pepper if necessary.    所有材料(除了芝士)煮至半熟，如需要用盐和胡椒调味。

Assemble

1. Put a layer of filling in the baking cup/bowl.    烤杯底层放些馅料。
2. Sprinkle some cheese on top. Then pipe in some mashed potato.    撒上芝士，再挤上薯泥。
3. Follow by a layer of filling, cheese and mashed potato. Lastly cheese on top.    接着一层馅料、芝士、薯泥。最后撒上芝士。
4. Bake at 180°C for 20 minutes..    以180°C烘20分钟。