Preheat oven to 375 °F.

Bring water to a boil in large sauce pan.

Thinly slice potatoes, add to boiling water and cook 5 minutes, drain and rinse with cool water; drain again.

Heat olive oil in medium skillet, add onions and garlic; sauté about 2 to 3 minutes until just starting to brown.

Add spinach, sauté 1 more minute.

Remove from heat and drain off liquid.

In a medium bowl, mix cheese with egg until well blended.

Add layers to 8 inch square baking dish as follows, using about 1/4 of each: pasta sauce, potato slices, sautéed spinach mixture and cheese mixture.

Repeat layers until all ingredients are used.

Cover with foil.

Bake about 35 to 40 minutes.