Spinach - Artichoke Squares

Nonstick cooking spray or olive oil

seasoned dry breadcrumbs

artichoke hearts, drained and squeezed of excess water (may also use frozen artichoke hearts)

package (10-ounce) frozen chopped spinach, thawed and squeezed of excess water

bunch scallions (white and light green part only), chopped

garlic, minced

shredded Swiss or Gruyere cheese

large eggs

mayonnaise

mascarpone cheese or 4 ounces softened cream cheese

half-and-half or whole milk

salt

Freshly ground black pepper,