A trio of sliders: (from left) curry fried chicken, bacon whiskey with arugula burger, and Maui onion with kewpie burger

Time was, you wouldn’t expect any remarkable effort from a kitchen trailer parked outside a brewery taproom. Particularly if its menu were limited to sliders and dirty fries. So, why have I driven to Bay Park, to order from a coral-colored car-hitch kitchen called Rosemarie’s?

Because we live in an age where tacos can be gourmet, sausages artisanal, and pizzas conjured with historical references baked in. Where a combination of celebrity chef culture, social marketing, and K-shaped economy have created conditions for miniature cheeseburgers to no longer treated as a culinary afterthought. Where the once-invisible roach coach line cook now dons a double-breasted chef’s frock, and the esteem that comes with it.

A trailer kitchen parked outside Harland Brewing Bay Park

From Wednesday through Sunday, Rosemarie’s does business outside of the Harland Brewing taproom, just across the freeway from Mission Bay. The cart is part of a catering business called Where to Eat California, which spins off pop-up and food truck brands largely centered around events dining.

Rosemarie’s schtick seems to have started with the idea of burgers made from ground brisket, and has expanded only as far as its tiny workspace allows: in addition to beef sliders, the cart offers morsels of fried chicken and steamed shrimp, likewise served on a little brioche. Mix and match two for $15, or three for $20.

One could probably make such a business work while embracing simplicity: basic beef, cheese, and pickle might do. But the dudes behind Rosemarie’s have embraced that nebulous concept of a chef-driven menu. In this case, that means burger toppings aren’t determined by a century of tradition, but actively curated, thereby evincing creativity, or at least greater care in choosing ingredients. Which could explain how I wind up with an order of dirty fries, topped by microgreens ($8).

Dirty fries topped with spicy sauce, pickled peppers, and micro greens

We’re not talking about low-brow food being made upscale — these remain crispy potatoes, slathered with rich condiments: either blue cheese and bacon crumbles, or chipotle and pickled peppers. Rather, it’s low brow food with slightly elevated aspirations. Still deep-fried, but with a low-key nutrient boost.

Obviously, the chef is making more impactful decisions when it comes to the sliders, the most important being to start with brisket, arguably the second-best tasting part of the cow (after ribeye). Other fine choices include making the fried chicken sliders with thighs (the juiciest parts of a chicken), and dressing burgers with Munster cheese, which melts more evenly than cheddar, and boasts a superior melted texture to American.

What’s remarkable is how much an impact subsequent decisions make. Rosemarie’s “classic” burger slider strays little from tradition, its subtle deviations boiling down to the use of Maui sweet onions and kewpie mayo (richer and creamier than regular). All the aforementioned components combine to make the most delicious burger I’ve ever eaten out of a mobile kitchen. I want more of this.

Which leads to a small shock, then, when the Little Sal burger delivers a distinct flavor shift, only by changing a couple of ingredients. Baby arugula and “bacon whiskey sauce” replace onions and mayo, somehow resulting in a sweeter and less memorable slider. With regard to the chicken sandwiches, the big difference in flavor hinges on the choice between a spicy, Nashville-style sauce, and a pungent, Indian-style yellow curry.

I’m no more ready for the switch to curried fried chicken than I am a sweet whiskey burger, and, subjectively, I’d contend Rosemarie’s is at its best when its chefs don’t color outside the lines. But it’s sure makes things more interesting that they do.