The Red Devils booked their spot in the quarter-finals of the FA Cup with a 3-0 win over League One side Shrewsbury on Monday night, but there was a touch of controversy about their second goal, which came from a Juan Mata free kick at the end of the first period.
Three Man United players were in offside positions when Mata made contact with the dead-ball, and Van Gaal has claimed that his side learned the technique from Midtjylland last week.
"We have learned because we analysed FC Midtjylland and we saw they were doing that. We thought it was always offside so we asked the referees and they said it's not offside, you can do that," Van Gaal told BT Sport. "That's why we have learned about the taking of the free kicks. Today we scored and that's good."
Man United will welcome Midtjylland for the second leg of their last-32 clash on Thursday currently trailing 2-1 from the first leg in Denmark.