Nielsen now works as an agent in Denmark, and he is reported to have organised the trial with his former club for the two Danish youth internationals.
Andreasen, 17, and Nissen, 16, both play for Esbjerg and the former has already made his first-team debut.
"They are young talents who have done very well so far," Nielsen is quoted by Bold.
"The trials came into being through my contacts with Spurs and it will be an exciting experience for them.
"Of course there is always a jump when you have to take the step from being a prospect, but for the future, they have great potential."