Whisk the 2 tsp of water and cornstarch together to form a slurry.
In a saucepan over medium low heat, add the hot sauce, garlic powder, worcestershire, cayenne, and salt and pepper. Then add in the cornstarch slurry. Whisk to combine.
Once the sauce starts bubbling, turn off the heat. Add 1 Tbsp worth of the vegan butter and whisk until fully melted. Repeat with another Tbsp worth of the vegan butter, and repeat until the entire stick has been whisked in.
At this point, your sauce should be super creamy and delicious. You can use it as is, or you can throw it in a high speed blender for 20 seconds. This will further emulsify the sauce and make it a bit thicker and creamier. I personally like it a lot, but do whatever you feel is best.
Immersion Blender Method
Whisk the 2 tsp of water and cornstarch together to form a slurry.
Melt the vegan butter (I do mine in the microwave until melted), then add everything including the cornstarch slurry into a jar / immersion cup. Blend with an immersion blender, slowly moving up to incorporate all the ingredients. After 30 seconds or so, you'll have a smooth sauce!
Add the sauce to a saucepan over medium low heat, and heat to activate the cornstarch slurry. Once it thickens you're done!