Read: Manchester United make Champions League return
Memphis, who was deployed in his favoured starting position on the left rather than as a traditional No. 10, showed the kind of form that led United to pay PSV Eindhoven a reported 25 million pounds ($39 million) for the 21-year-old in May.
"When you score a goal then you are the hero," Van Gaal told reporters.
"I want to kiss him tonight, because when you score two goals and give an assist also, then normally in the world you are the hero," the manager added.
United left back Luke Shaw, who along with Memphis was one of the best players on the pitch, also praised his team mate's performance and first goals for the club.
"Of course I am really happy for him today," the England international said.
"Now he's off the mark, hopefully it can bring him many more goals.
"I think our relationship is starting to build up. We have played a couple of games together and I am starting to understand how he wants to play," he added
"It is great to be playing with him, he can beat a man and he likes the attacking support from me as well -- which is something I like to do," the 20-year-old said.
Shaw also hailed the importance of Memphis's late assist for Marouane Fellaini, which ensured that United take a two-goal cushion into the crucial second leg.
"We knew that we needed one more goal to make us feel more comfortable when it comes to the next game," Shaw said.
"The Fellaini goal was massive for us, we are glad we got that and now we can look forward to next week," he added.
Fellaini acknowledged that his late header was important, but insisted that United still had work to do when they visit the Belgian club in the return leg on Aug. 26.
"I think it was important to score a third goal and we did, so that's fantastic," the 27-year-old Belgium international said.
"It's a win but now we have to be careful in Bruges. Normally it would be not easy, but we have the quality to win there as well," he added.
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