Cover the soy curls in water and rehydrate them for 10 - 15 minutes. Then drain them and squeeze out as much water as possible.
While they rehydrate, make the marinade by combining the remaining ingredients in a bowl.
In a skillet over medium heat, add the soy curls and cook them for about 3 - 5 minutes to dry them out a bit more. Then pour over the marinade and stir to combine.
Cook the soy curls until most of the liquid has reduced down and they are a nice dark brown color. This should take about 10 minutes. You can add more browning sauce if you like.
Season to taste, adding in anything else that you like. Remove from pan and reserve.
In a bit of oil, grill the onions until translucent and slightly browned, about 6 - 8 minutes.
Add the soy curl steak back in, final season to taste. Cover and keep warm on low.
Cheese Whiz*
Soak the raw cashews in boiling water for 10 - 15 minutes (you can actually do this before making the soy curls steak so cashews are ready when you're done with the steak).
Blend the drained cashews with the unsweetened plant milk in a high speed blender until smooth.
Add everything but the cheese shreds to a saucepan over medium heat, whisk to combine and bring to a light boil. Add cheese shreds and whisk until melted. Taste and adjust for seasoning, and add more plant milk if the sauce is too thick.
Load up your sandwich roll with as much steak and whiz as you like and enjoy!
Notes
*I've found that different brands of vegan cheese will result in thicker or thinner sauces, so if yours is too thick, simply add more plant milk until it's at your desired consistency.