The Norwegian star was in scintillating form as she seared to victory in both the women's 10km F and 10km C pursuit events, holding off Russia's Natalia Nepryaeva to sit at the summit of the World Cup table with 1,409 points.
Johaug's compatriot Ingvild Flugstad Oestberg finished third in Sunday's 10km C Pursuit, beating fellow Norwegian Heidi Weng to the final spot on the podium with a time of 27:55.7minutes.
But it was Johaug who triumphed in the Czech mountains for her ninth race victory of the season with a time of 26:49.7minutes, now lying a considerable 457 points ahead of Weng in the World Cup standings and 470 clear of Nepryaeva who sits in third.
Krista Parmakoski finished fifth in Sunday's event in a surprise result for the Finnish skier, as the USA's Jessica Diggins – who is fourth overall – languished back in tenth place.
Alexander Bolshunov emulated Johaug's exploits in the men's event, adding a 15km C Pursuit victory on Sunday to his 15km F glory achieved the day before.
The Russian star, whose lead on top of the overall table now stands at 159 points, stopped the clock in 37:01.3minutes, beating Norway's Johannes Hoesflot Klaebo to the line while Simen Hegstad Krueger came third.
Klaebo is now second in the World Cup standings with 1,122 points, while Sergey Ustiugov – who did not take part in the event because he recently became a father – is in third.
Sjur Roethe finished fourth in Sunday's event, while Iivo Niskanen crossed the line in fifth to keep him in fourth place in the overall table.