Cut the tempeh into 1/2 inch cubes and transfer them to a food processor. Blend the tempeh for about 5 seconds, until you get very small pieces of tempeh. When you open the lid of your food processor, you will get a good whiff of the odor from the fermented soy beans, and that's perfectly okay.

In a bowl, mix the vegetable broth, soy sauce, maple syrup, garlic powder, and ground coriander.

Heat a nonstick skillet or sauté pan over medium heat. Add the tempeh and the broth mixture. Cook for about 8 to 9 minutes, stirring occasionally, until the liquids have completely absorbed into the tempeh. The tempeh might look like it's ready to be pulled off the stove in 5 minutes, but resist the urge to do so. When you tap the tempeh with the back of a spatula, and you can hear a sound that is similar to walking through puddles in the rain, it means the tempeh is not ready yet. You are probably a few minutes off. Once the liquid has been absorbed, remove the pan from heat.

Assemble the lettuce wraps. Fill the lettuce leaves with the carrots, cabbage, red bell pepper, and some of the tempeh. Drizzle peanut sauce over the filling and garnish with sliced scallions and red pepper flakes, if you desire. Serve immediately.