minecraft-assets/assets/minecraft/models/block/mushroom_block_inside.json

{
    "ambientocclusion": false,
    "textures": {
        "texture": "block/mushroom_block_inside",
        "particle": "block/mushroom_block_inside"
    },
    "elements": [
        {   "from": [ 0, 0, 0 ],
            "to": [ 16, 16, 0 ],
            "faces": {
                "north": { "texture": "#texture", "cullface":"north" }
            }
        }
    ]
}