@bot.event
async def on_guild_channel_create(channel):
    guild = channel.guild
    embed = disnake.Embed(color=disnake.Color.dark_gray(), title = "", description = f'`{channel.name}` **Was created**')
    embed.set_author(name=guild.name, icon_url=guild.icon.url)
    embed.add_field(name="", value=f':house: Created channel: `{channel.name}`', inline=False)
    embed.add_field(name=f"Responsible Moderator: {}", value = '')
    embed.set_footer(text=f"Legione Straniera • Date of creation: {datetime.now(tz=moscow_tz).strftime('%B %d, %Y %H:%M')}")
    await disnake.utils.get(channel.guild.text_channels, id=1240402311147290685).send(embed=embed)

embed.add_field(name=f"Responsible Moderator: {}", value = '')

I need to mark the creator of the channel as in member.mention.

I tried to do it through the guild.get_member but unsuccessfully.