Teenager Erling Braut Haaland scored twice more off the bench on Friday as Borussia Dortmund moved up to third in the Bundesliga with a 5-1 thumping of Cologne.
Having claimed a hat-trick as a replacement on his Dortmund debut last Saturday to inspire a 5-3 win away at Augsburg, Haaland, 19, again showed clinical finishing.
"For Erling, it's simply wonderful - five goals, two games, there are worse starts," said Dortmund captain Marco Reus.
"Especially here at home - that's why we signed him.
"That was a good step forward from us -- also from me personally," added Reus who was criticised for missing clear chances against Augsburg.
With his team 3-1 up, Haaland came on for his first home appearance with an hour gone and 11 minutes later was on the scoresheet, slamming home the rebound of a saved Julian Brandt shot.
He then showed his speed to beat Cologne goalkeeper Timo Horn, tucking the ball into an empty net on 87 minutes.
Dortmund coach Lucien Favre explained why Haaland was again only a second-half replacement.
"He didn't train in December due to injury, therefore we have to be careful with him," said the Swiss.
"He's not ready to play from the start, we have a plan for him."
The result leaves Dortmund level on 36 points with defending champions Bayern Munich and four behind leaders RB Leipzig.
Goals by Raphael Guerreiro and Marco Reus gave Dortmund a 2-0 half-time lead.
England winger Jadon Sancho grabbed a third after the break and Cologne striker Mark Uth claimed his first goal for the visitors before Haaland's entrance.
The teenager has 33 goals in 24 games this season having netted 28 times for Salzburg before Dortmund snapped him up for 20 million euros ($22 million) last month.
Dortmund were ahead with less than a minute gone at Signal Iduna Park as Sancho threaded a pass through to the unmarked Guerreiro who slotted home a first-time shot.
It was Dortmund's fastest goal this season.
The hosts dominated and were awarded a penalty, which was reversed when VAR took a long look at defender Sebastian Bornauw's lunging tackle on Dortmund's Achraf Hakimi before deciding the foul was just outside the area.
Mats Hummels then clattered the woodwork with a thumping header.
However, Dortmund went into the break 2-0 up when Hummels long-range pass put Reus in behind the defence.
The Germany winger showed great timing to sweep the ball into the net on 29 minutes.
Cologne's Colombia striker Jhon Cordoba hit the post with Dortmund goalkeeper Roman Burki beaten just before Sancho grabbed the hosts' third.
Reus slid the ball into the path of the England winger, who slipped his marker and fired home four minutes after the break.
With an hour played, Uth claimed his first goal for Cologne when the ball fell to him unmarked on the left.
However, the scene was set for Haaland to claim his two goals with Cologne's defence tiring and unable to cope with the towering teenager's runs.
"He's living his dream right now, we don't want to wake him up," joked Dortmund's sports director Michael Zorc.
"He's trained well this week and is incredibly ambitious. He wants to score every goal possible in practice and gets really angry if he doesn't take a chance.
"He's got a really good mentality. That's why we signed him."
Norway striker Erling Braut Haaland, 19, has five goals in two league games after scoring twice in Borussia Dortmund's 5-1 win over Cologne on Friday.