What Tolkien says about Lembas
-They contain  honey
-they are light-colored on the inside and light brown crust
-they are thin and regular-shaped. This implies they were made on some kind of griddle iron. The closest modern equivalent is a Krumkake iron. I used a pizzelle iron

Some other things we can guess.
They contain the fruit and maybe the flower-water of the Mallorn tree. I substituted oranges, although kumquats or a hand of Buddha fruit might be better.
They probably had some kind of finely ground light-colored nut in them. I used almonds.
They contained some kind of nourishing flour. I used semolina flour, which is a more primitive flour, and also more nourishing.
Galadriel probably used some kind of grinder to refine the ingredients. I used a blender.

The recipe:
3 eggs
1 cup honey (preferably wild honey)
1 tablespoon grated orange peel or three kumquats or one large finger of a hand of Buddha.
2 teaspoons orange flower water (optional)
3 oz blanched almonds
1/4 cup melted butter
2-1/4 cups semolina flour
1/2 teaspoon salt

Place eggs, honey, orange peel or other fruit, orange flower water, and almonds in blender. Blend on high for 3 minutes. Add 1 cup of the flour. Blend for 1 minute. Scrape into a bowl and add remaining flour and salt. Whisk or stir until well blended. Bake lembas on a pizzelle or krumkake iron 15 seconds each or until lightly brown. You may substitute a waffle iron but add a teaspoon of baking powder. The texture will not be quite accurate in a waffle iron.