my %HoHCopy = map
  { $_ => $HoH{$k} }
  grep {
    $HoH{$_} and values %{$HoH{$_}}
  } ( keys %HoH );

# or 

my %HoHCopy = map
  {
    ($HoH{$_} and values %{$HoH{$_}})
    ? ($_ => $HoH{$k})
    : ()
  } ( keys %HoH );