如何使用NHibernate QueryOver实现带排序的分组查询？

我需要用NHibernate QueryOver实现如下SQL的功能：

SELECT TOP 10 * from 
            (SELECT aColumn, min(WorkingDay) as d
                FROM   aTable
                GROUP  BY aColumn) as a
    ORDER  BY a.d asc

这段查询的核心是对分组后的结果进行排序。我已经写出了子查询的代码：

var subquery = QueryOver<aTable>.Of(() => alias)
    .Select(
    Projections.ProjectionList()
    .Add(Projections.Group<aTable>(p => p.aColumn).WithAlias(() => alias.aColumn))
    .Add(Projections.Min(() => alias.WorkingDay).WithAlias(() => alias.WorkingDay))
    );

但不知道怎么构建对应的外层查询，希望能得到帮助。

更新：
在Firo的帮助下，最终的查询代码如下：

aTable t = null;
var min = Projections.Min<aTable>(p => p.WorkingDay).WithAlias(() => t.WorkingDay);
items = await s.QueryOver<aTable>(() => t)
    .WhereRestrictionOn(f => f.State).IsIn(states)
    .Select(Projections.ProjectionList()
        .Add(Projections.Group<aTable>(p => p.aColumn).WithAlias(() => t.aColumn))
        .Add(min)
        )
    .OrderBy(min).Asc
    .TransformUsing(NHibernate.Transform.Transformers.AliasToBean<aTable>())
    .Take(10)
    .ListAsync();

内容的提问来源于stack exchange，提问作者Peter Larsen 'CPH'