Portillo’s chocolate cake is one of Chicago’s most iconic desserts — a two-layer devil’s food cake that the restaurant has been making the same way since the 1960s. The recipe that makes it worth shipping overnight from Chicago is also the recipe that most home copycats get wrong: full-fat mayonnaise instead of oil. Here’s how to make it correctly at home for about $12.
The One Thing That Makes This Cake Different
Every major recipe for Portillo’s chocolate cake confirms the same ingredient: one cup of full-fat mayonnaise in place of oil.
This is not a mystery variation or a rumor. WGN Radio reported it. Chicago Parent tested it. Portillo’s has never disputed it. The reason it works is that mayo is already an emulsion of oil and eggs, so replacing the oil with mayo means you’re adding fat (moisture), additional egg proteins (structure), and a small amount of acid (better rise) all at once. The result is a cake that stays moist for three to four days — longer than any oil-based box cake.
The critical failure mode: using light mayo or fat-free mayo. Both remove the fat that does the actual work. Use full-fat Hellmann’s, Duke’s, or Best Foods. Nothing else.
Why Two Full Cans of Frosting
Portillo’s chocolate cake is generously frosted — the layer between the cakes is thick, and the outside is fully covered with a substantial coat. One can of frosting produces a thin, patchy result that looks nothing like the original. Two full 16-oz cans of Betty Crocker Rich & Creamy Chocolate Fudge is the correct amount. Don’t reduce it.
The Most Important Step: Full Cooling
More home copycats are ruined by impatience than by wrong ingredients. Frosting a warm cake melts the frosting immediately — it slides off the sides, creates a gluey middle layer, and never sets properly. The layers need to cool completely: 15 minutes in the pan, then at least 90 minutes on a wire rack (or 30 minutes room temp + 30 minutes in the refrigerator). Touch the bottom of the cake — it should feel completely room-temperature, not just cool on top.
Box Mix vs. From Scratch
Portillo’s uses Betty Crocker Devil’s Food Cake Mix — this has been widely reported and never denied. The box mix version produces the authentic result. If you prefer scratch baking, the FAQ above includes a from-scratch version using Dutch-process cocoa, flour, and the same mayo base; it’s excellent but produces a slightly different (darker, more intensely chocolate) crumb than the original.
Making the Cake Shake
Once you have this cake on hand, the Portillo’s Chocolate Cake Shake — their other famous item — becomes easy: blend one cold slice with one cup of vanilla ice cream, pulsing 3–4 times. The chunk texture is the whole point; don’t over-blend.
