Position a rack in the top third of the oven and preheat the broiler.

• Wipe the tops of the portobello mushrooms with a damp paper towel to remove any dirt. Remove the stems and set aside for the gravy; using a spoon, gently scrape the black gills from the undersides of the caps. 

Place the mushrooms, cap sides up, on a sheet pan. Broil on the top rack of the oven, turning the mushrooms halfway through, until lightly browned, about 10 minutes. Remove the mushrooms from the oven and let cool slightly. Drain off any excess liquid, then using a paper towel, gently pat the mushrooms on both sides to remove any additional moisture. While the mushrooms are broiling, prepare the broccoli leaves.

• Strip the broccoli leaves from the stems; coarsely chop the stems and thinly slice the leaves, keeping them separate. 
• Peel and thinly slice enough onion to measure ¾ cup [1½ cups]; set aside ¼ cup [½ cup] for the gravy. 
• Set aside half the garlic-herb blend for the gravy.

In a medium sauce pot over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the broccoli leaf stems, ½ cup [1 cup] onion, and half the garlic-herb blend and season lightly with salt and pepper. Cook, stirring occasionally, until the vegetables start to soften, 2 to 3 minutes. 

Add the broccoli leaves and ½ cup [1 cup] beer, white wine, or water and bring to a simmer. Cover, reduce the heat to medium, and cook, stirring occasionally, until the leaves are wilted and the stems are soft, 8 to 10 minutes. Remove from the heat and season to taste with salt and pepper. While the broccoli leaves are cooking, finish the mushroom “steaks.”

• Crack the egg into a shallow bowl, season with salt and pepper, and beat with a fork until just blended.
• On a plate or shallow bowl, season the Parmesan with pepper and spread in an even layer.

Working with 1 mushroom at a time, gently squeeze out any remaining liquid. Dip the mushroom into the egg; let the excess drip off, then gently press the mushroom into the Parmesan, coating both sides. Repeat this process, dipping the mushroom into the egg and then pressing into the Parmesan, coating the mushroom thickly with Parmesan.

In a large frying pan over medium heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the mushrooms and cook, turning once, until golden brown, 1 to 2 minutes per side. Transfer to a paper-towel-lined plate. Do not clean the pan. 

• Coarsely chop the mushroom stems.
• In a small bowl, using a fork or whisk, mix together the mushroom gravy blend, remaining garlic-thyme blend, and 1 cup [2 cups] beer, white wine, or water to form a slurry.

In the same pan used for the mushroom “steaks,” warm 1 to 2 tablespoons oil until hot but not smoking. Add the mushroom stems and remaining sliced onion, season with salt and pepper, and cook, stirring occasionally, until starting to soften, about 2 minutes. Stir the gravy blend slurry to recombine, then add the slurry and cook, stirring occasionally, until the gravy is thickened, about 5 minutes. Remove from the heat and season to taste with salt and pepper.

Transfer the broccoli leaves to individual plates and top with the mushroom “steaks.” Pour the gravy over the mushrooms and serve.