Kohlrabi and Potato Gratin

My husband and I returned to our hometown this weekend, and returned to Madison with a ridiculous amount of kohlrabi.  I started thinking about what I could make tonight to use it up, and I came up with this delicious gratin recipe.  Really, it doesn't require BOTH kohlrabi and potatoes, but rather could be made with exclusively one or the other.  If you aren't vegetarian inclined, I saw many gratin recipe ideas out there that included cooked bacon or ham, which you could definitely try.  I think it's perfect as is.

We had this with a light salad with lettuce, green pepper, tomatoes and chick peas.

I apologize again for the poor quality of my photos.  My camera is still broken.

Ingredients:

4-6 small to medium kohlrabi, cleaned and pealed
2 large baking potatoes, pealed
1 small onion finely chopped
4 cloves garlic, finely chopped

5 cups milk
1 cup half and half
5 tablespoons flour
4 tablespoons butter
1 cup shredded Gruyere cheese (any type of Swiss cheese would be nice, or even Parmesan)
2 teaspoons thyme
pinch nutmeg
salt and pepper

Directions:

First halve kohlrabi, and then use a mandolin, food processor, or just a knife to slice kohlarabi and potatos into 1/4 inch slices.  Heat olive oil in dutch oven, or heavy bottomed pan with deep sides.  Cook onion over medium high heat until beginning to become translucent.  Add prepared kohlarabi, season with salt and pepper, and add a few tablespoons of water to help steam kohlarabi.   Put a lid on the pan, and cook over medium high heat until kohlarabi is approximately half way cooked, adding water as needed.  For me, this took between 20 and 30 minutes.  Kohlarabi will take a longer period of time to cook than the potatoes, so try to do your best to time it right.  Of course, you are going to smother this entire thing in cheesy, creamy sauce, so it will cover up any mishaps.  After the kohlarabi is half way cooked, add the potato and garlic, and continue to cook until everything is fairly soft. Take the lid off and allow the water to evaporate, if there's any.  Add some salt to the mixture.

While you are waiting for the kholarabi to cook, make the sauce.  First, melt the butter in a sauce pan over medium heat.  Add pepper, some salt, and the flour.  Stir with a whisk and cook for 1-2 minutes.  Add the milk, and cook, whisking frequently, until the mixture begins to very lightly boil.  At this time, add the half and half.  Once the mixture is lightly boiling again, add the cheese, and remove from heat.  Taste for saltiness.  It will take a surprising amount of salt to get anywhere with it, and the mixture should be VERY SLIGHTLY over salted by the time you're done.  If you are nervous about this judgement, just add salt to your plated food if you need it (it's better to err on this side than on the too salty side). 

Once both components are ready, pour the cheese mixture over the kohlrabi/potato mixture (either in the dutch oven you cooked in, or in a separate baking dish).  Sprinkle bread crumbs over the top if desired.  Cover and cook in a 350 degree oven until the mixture is bubbling around the edges.  Take the lid off and cook 10 minutes more.  Allow to cool at room temperature for 10 minutes to allow the mixture to set up before serving.