Place all ingredients, except olive oil, in food processor and pulse until mixture consists of fine pieces; with the machine running, gradually add the olive oil and process to a paste. Place pesto in a covered container & refrigerate until use. Yields 1 cup.
De-stem the mushrooms with a knife & scoop out the gills with a teaspoon. Brush both sides of the caps with olive oil (be generous), season with salt and pepper, bake @ 400º for about 10 minutes.
Now dredge the mushrooms. You need three dishes (flour, egg wash, bread crumbs). Dredge a cap in the flour, then dip in the egg/milk combo, then dredge again in the breadcrumbs.
Now, fry. Heat a skillet (12") with the oil to 325º. Fry the mushrooms, 2 at a time, for about 2 min. per side. Put on a paper towel.
Assemble: Use your favorite bread (I like focaccia). Use the pesto, some provolone cheese, and the shroom. Put in the broiler to melt the cheese.