Step 1

Roast the jalapeños. You can do this over a gas stove, in a dry cast iron pan, or under your oven broiler. Roast until the skin on the outside is black and blistering. Remove from the heat, place in a bowl and cover with a kitchen towel or plastic wrap for 10 minutes. Once they're cool to the touch, peel off the skins (you can use your hands or a knife - it should come off fairly easily).

Step 2

Remove the stem and seeds of your jalapeños and place them in a blender with the cashews, water, vinegar, shallot, garlic, cucumber, lemon, salt and pepper. Blend until smooth and creamy, adding more water if necessary to get your blender moving. Taste and adjust seasonings, adding more salt, pepper or lemon to your liking. Stir in the chopped chives. Chill until ready to use.

Step 3

Slice the portabello mushrooms. Place them on a plate and drizzle them with olive oil, soy sauce, balsamic and freshly ground black pepper. Use your hands to coat the mushrooms on all sides.

Step 4

Heat a grill or grill pan to medium-high heat. Grill the mushroom slices on both sides until char marks form, about 3-4 minutes per side.

Step 5

Assemble tacos with mushrooms, avocado, cabbage, cilantro, sliced jalapeños, if using. Serve with jalapeño sauce.