When I tried this recipe pre-dinner party, the individual pieces looked very large. I tried slicing (see photos) and found this not only looked much more attractive but allowed the option for guests to adjust their serving size to their appetite.
The following recipe serves 2 - adjust quantities for expected number of guests.
2 t olive oil (heat first)
1 small shallot, peeled and finely minced, until golden brown, then add:
6-8 (3-4 oz.) mushrooms (I use crimini, baby bella, shitake or a mix of these)
and continue cooking 2-3 minutes over medium heat, then add:
4 oz spinach (if not using baby spinach remove stem, including vein that runs down the middle of the leaf and tear into small pieces) and cook just until spinach wilts.
Separate, if necessary:
2 boneless, skinless chicken breasts, ~3/4 to 1# total
then slice lengthwise down the middle, almost but not completely through, to form a large pocket
Place the chicken on a washable plate, plastic cutting board or wax paper and open each piece so the two sides lie flat. Place 1/2 of the mushroom - spinach mixture on each piece. Then place, lengthwise on top of the center of the mixture
2/3 - 1 oz of goat cheese (I use goat cheese with herbs).
Then fold the pieces together. Chicken breasts can be prepared to this point and refrigerated for several hours. The following step should be done preferably no more than an hour or two before baking.
Dip each breast piece (both sides) in:
1 egg, beaten (I have on occasion used 1/8 c "egg product" - 1 egg will actually do 4-6 pieces - but I think in this case using the real egg is better)
and then immediately (again, both sides) in:
~1/3 c panko (more or less depending on size of chicken; I usually use Whole Food's spinach panko but have also used their lemon-herb panko and sun-dried tomato panko). Place on non-stick or (olive) oiled cooking pan. If not cooking immediately return to refrigerator.
Serve individual pieces plated...
Garnish with fresh thyme sprigs (optional).
I often serve with Weeds with Pecans and Fruit and a wild/brown rice mix.