Spray a 9x9 inch baking dish with non-stick spray. Slice whole canned green chiles wide open; rinse out any seeds, then drain. Arrange half of the chiles in the bottom of the dish.

Sprinkle chiles with half of the grated jack and cheddar cheeses. Add remaining green chiles in another layer on top of the cheese. Top with remaining jack and cheddar cheeses.

In a small bowl, whisk together eggs, flour, milk, and salt until fully blended. Pour this mixture over the casserole, distributing evenly.

Bake casserole uncovered at 350 degrees for 30-35 minutes, until golden brown on top. Remove dish from oven and transfer to a wire rack.

Let it cool for a few minutes, then slice casserole into 6 equal sized pieces, serve, and enjoy!