NEW YORK ( TheStreet) -- If you want to define "chipotle," as in Chipotle Mexican Grill ( CMG), just take look a the company's stock price, which is up close 20% over the past three months and is up 50% year-to-date. At a price-to-earnings ratio of 46, more than twice the valuation of Yum! Brands ( YUM), these shares carry some eponymous heat.I don't deny that Chipotle has built itself into a leading fast-casual restaurant that's posting strong growth and above-average margins. To the extent that the company now deserves a P/E that is almost 3-times that of McDonald's ( MCD), I don't believe it does. Not to mention this leaves absolutely no margin for error in an environment where discretionary remains unstable. TSN). If anything has kept the stock sizzling, it's been Chipotle's strong restaurant-level margins, which registered an astounding 27.6% in the July quarter. While that number is significantly higher than both McDonald's and Yum! Brands, I did notice a 160-basis point decrease. Chipotle has called that a "trivial" decrease. But let's not forget that it was preceded by 110-basis point decrease in the April quarter. Now, I don't want to make too much this, but should restaurant-level margins decrease again on Thursday, it then becomes a trend. My issue here is that, while Chipotle's overall profit margins still remain high relative to its quick-service peers like Panera ( PNRA) and Qdoba, which is owned by Jack in the Box ( JACK), this is because Chipotle operates a premium-priced restaurant.