Sweet Potato Banh Mi
Crisp, tender, crunchy, rich, creamy, sweet, sour, spicy, this sandwich has got it all (and with no meat, to boot!).
Step 1: Make the Do Chua
Do chua (full recipe here) is the lightly pickled carrot and daikon slaw you find inside a Vietnamese sandwich (or occasionally served as a side dish). It's made by cutting carrots and daikon into thin julienne (a mandoline can help), and massaging them with salt and sugar until they go limp. I use a quarter cup sugar and a tablespoon of kosher salt for every quart of julienned vegetables (about a pound).
Once the vegetables are softened, I add a mixture of water and rice vinegar (a cup of water to a half cup of vinegar). The pickles can be used immediately, but will get better if you...
Pack it Up
... let them rest for at least a few days. I keep mine in a sealed mason jar in the fridge. Over the course of a few days, the vegetables will become more aromatic and pungent, while still retaining their crispness.
Step 2: Make the Ginger-Scallion Oil
I first saw ginger-scallion oil being used on a banh mì at the awesome Banh Mì Ba Le in Dorchester, MA. To make it, place chopped scallions and grated ginger in a bowl, then heat up some oil. In this case, we're going to be frying sweet potatoes, so I just use oil directly from the wok I'm going to cook it. Once the oil is hot...
Pour It Over
...pour it on over. The scallions and ginger will sizzle briefly, then settle down. Season the oil with salt and pepper. This stuff will keep in the fridge for weeks, and is excellent on all sorts of things. Sandwiches, eggs, meats, you name it.
Step 3: Gather Ingredients
Once your condiments are made, gather the rest of the ingredients and have them on-hand. Maggi seasoning, a ripe avocado, crisp seedless cucumber spears, slivered jalapeño pepper, cilantro sprigs, and a good soft, crusty roll, preferably a Vietnamese baguette.
Step 4: Dip'em
Frying the sweet potatoes in a tempura-like batter is the key to this sandwich. It adds texture to the mix, along with plenty of porous surfaces for that ginger-scallion oil to seep into. The key to a light tempura is to cut your flour with cornstarch or rice flour (to lower protein content and inhibit gluten development), and to use ice-cold soda water to moisten it. Gluten doesn't develop as well at cool temperatures, keeping the batter nice and light, while the bubbles from the seltzer further aerate and lighten it. For an extra crisp batter, you can substitute part of the seltzer water for vodka, which vaporizes faster and further inhibits gluten formation.
Step 5: Fry'em
Once coated in batter, Fry the sweet potatoes in hot oil, making sure to agitate them vigorously as they cook. Keeping a fresh supply of oil swirling around the potatoes leads to crisper end results, as no pockets of hot or cool oil will develop in the pan.
Step 6: Drain
Drain and season the potatoes on paper towels.
Step 7: Construct
Start construction by splashing some liquid aminos (such as Maggie or Bragg's—you can also use soy sauce) on the bread, then laying your avocado across both sides of the split toasted baguette. As Erin says, "avocado is like vegan butter." Spoon a bit of ginger-scallion oil on top, making sure to use enough to allow it to soak into the bread slightly.
Add your fried sweet potato, along with some more ginger-scallion oil, followed by the do chua, cucumber spears, jalapeño slivers, and cilantro sprigs. Close that sucker up (carefully), and get ready.
Step 8: Eat
This is a heck of a lunch, whether you're a meat-eater or not.