Step #2 Arrange the baguette slices on 2 baking sheets; bake baguette slices at 375° for 8 mins or until crisp.
Step #3 Preheat broiler.
Step #4 Place 1/2 (1-oz) bread slice in a food processor/blender; pulse 10 times or until coarse crumbs measure 1/4 c.
Step #5 Drain the oysters in a colander over a bowl, reserving 2 tbsps oyster liquid.
Step #6 Place the oysters on a broiler pan, & broil 7 mins or until the edges of oysters curl.
Step #7 Cool & chop.
Step #8 Place onions, celery, & parsley in a mixer or food processor/blender, & process until finely sliced.
Step #9 Melt butter in a Dutch oven over medium-high heat.
Step #10 Add onion mixture; sauté 5 mins or until tender.
Step #11 Add spinach; cook 2 mins or until thoroughly heated.
Step #12 Stir in oysters, 2 tbsp oyster liquid, 1/4 c breadcrumbs, cheeses, & the remaining ingredients; cook 2 mins or until well mixed, stirring constantly.