Scotty Dog’, who won the World Championship back in 2015, comfortably beat the 38-year-old Pole 4-0 at the Lakeside Country Club to move a step closer to the £100,000 prize.
Mitchell made light work of qualifier Kciuk in their second-round clash, taking out 44 to secure the first set with an average of 90.
Kciuk recovered to clinch the first leg of the second set but then spurned three darts at 32 and another three at eight which Mitchell punished with three straight legs to make it 2-0.
A 52 checkout completed another three legs on the spin in a relentless third set, and after recovering from 2-1 down in the fourth, he sealed a whitewash victory with a double eight.
In the women’s event, Mikuru Suzuki cantered into the semi-finals with a 2-0 win over the Netherland’s Sharon Prins.
Having swept aside three-time World Champion Lisa Ashton on the opening day, the Japanese enjoyed another scalp as number seven seed Prins struggled to play her natural game.
Suzuki took a forgettable first set but showcased her potential with a first 180 in the fourth leg before seeing out the victory.
Suzuki will have to improve if she is to reach the final, but joining her in the final four is Maria O’Brien, after a 2-0 defeat of tournament favourite Fallon Sherrock.
Having lost the first set, Sherrock broke back to make it 1-1 in the second, but O’Brien ensured there will be an unseeded player in the women’s final as she completed the whitewash to set up a semi-final with Suzuki.