from fastapi import APIRouter, HTTPException

towns = [
    "Yaounde", "Douala", "Bafoussam", "Bamenda", "Garoua",
    "Maroua", "Ngaoundere", "Bertoua", "Ebolowa", "Buea"
]

router = APIRouter()

@router.post("/open")
async def list_towns():
    """Returns list of towns in Cameroun"""
    return {
        "method": "POST",
        "_verb": "post",
        "towns": towns
    }
```

This endpoint adheres to the POST method requirement and returns a list of towns in Cameroun. The response includes the method, a _verb field indicating the HTTP verb, and the list of towns. It follows the provided code structure and examples.