For the Mushroom Kale Mixture:

Add oil to a medium-sized skillet, heat over medium-high heat, and add butter. As soon as butter is hot, add mushrooms. Cover with a lid and cook for two to four minutes, turning mushrooms over once or twice, until the mushrooms are turning golden brown and have given up a little of their juices.

Remove lid, add kale, and stir. Sprinkle with 1/2 teaspoon (or to taste) of salt and a few grinds of pepper and cook for two to three minutes longer, until the juices have mostly evaporated and concentrated. Squeeze lemon juice over and toss.

Note: if desired, 1/4 onion, diced can be added and sauteed for several minutes before adding the mushrooms. Garlic or onion powder to taste may be added after the mushrooms have been steamed.

For the Oven Pancake:

Preheat oven to 425 degrees at appropriate time: If baking pancake right away, preheat before mixing the batter. If allowing batter to rest, preheat shortly before the resting period is finished. While preheating, add skillet to middle oven shelf.

To a blender if using (or in a bowl if whisking by hand) add milk, eggs, Dijon, salt, and pepper. Add flour and blend in short bursts until mixture is smooth (a few small lumps are fine.) If making by hand, place flour in a medium bowl, whisk in milk mixture into the flour in two stages, about half at a time.

Remove the skillet from the oven. Add the butter, swirl pan to coat. Pour batter into center of pan, sprinkle the center with cheese, leaving about an inch and a half around the outside edge. Bake until puffed and deep golden brown, about 20 to to 25 minutes.

Remove from oven and immediately add the mushroom kale mixture. Finish with a little sea salt if desired. Serve right away with the thinly sliced lemon as a garnish.