Potato and Tomato Gratin

Total time: 1 hour 15 minutes
    We are planning for leftovers with this gratin.  I normally use Gruyère in potato gratins but I decided to use something stronger with the sage and tomatoes.  Use what ever cheese you like - a sharp cheddar could be good, or Muenster.  And, Yes, tomatoes do work well with potatoes!

 Ingredients:

• 4 medium potatoes, 22oz total (660gr)
• 1 large onion or 2 smaller onions,  12oz total (360gr)
• 2 - 3 tomatoes, 12 - 14oz total (360-420bg)
• 2 cloves garlic
• 1 tbs olive oil
• 3oz (90gr) strong cheese of choice,  I used Tomme  shredded or cut into small pieces
• 1 tbs dried sage
• 1/4 cup chicken stock
• 1/4 cup grated Parmesan

 Instructions:

• Thinly slice the onions and garlic. 
• Heat oil in a medium skillet over medium-high heat.  Add onions and garlic and sauté until tender and just starting to brown, about 10 minutes. 
• Remove from heat and set aside. 
• With a sharp knife thinly slice the potatoes, or use a mandolin (if you think this is a musical instrument, you don't have one. ) 
• Slice the tomatoes as thin as the potatoes (you should get 8 - 10 slices per tomato). 
• In a glass or ceramic baking dish just large enough to hold ingredients  (I use an 8" X 11" (20 X 27.5cm) oval baking dish) lay 1/3rd of the potatoes. 
• Spread half of the sautéed onions over the potatoes. 
• Add a layer of tomatoes, touching but not overlapping. 
• Spread half of the cheese on the tomatoes and sprinkle with half of the sage. 
• Repeat layers once.
• Top with remaining 1/3 of the potatoes. 
• Pour the stock over all, sprinkle with Parmesan, cover with foil and bake at 425F (210C) for 40 minutes. 
• Remove foil, reduce heat to 400F (200C) and continue baking another 20 minutes. 
• Remove from oven, let rest 5 - 10 minutes, cut and serve.