Potato Butternut Squash Au Gratin with Sage Pesto and Toasted Hazelnuts

 This Potato Butternut Squash Au Gratin is a nice twist on a classic au gratin. The hazelnuts add a nice crunchy top and the butternut squash lightens it up while the sage pesto brings on a whole new richness.

I wanted to make a au gratin that was a bit lighter and healthier than the classic style.  Although it still has cheese and a little butter I used 1% milk instead of half and half and hazelnuts instead of bread crumbs.

Potato Butternut Squash Au Gratin

Gratins originated in France.  It is a dish that has a golden crust on top typically from the addition of either bread crumbs or cheese and are served in a shallow casserole dish.

Potato Butternut Squash Au Gratin

This gratin goes with a Riesling, Gewürztraminer, Pinot Gris, Verdejo, Rose, Pinot Noir, Merlot, Red Rioja or a Petite Sirah

  Potato Butternut Squash Au Gratin Recipe:
8 – 10 Servings
Toasted hazelnuts
  • 1 Cup Toasted Hazelnuts – ground (can substitute almonds or panko bread crumbs)
 Sage Pesto – About 1 Cup
  • 1 Cups Fresh Sage
  • 1/2 Cup Toasted Walnuts
  • 1/2 Cup Asiago Cheese
  • 2 Tablespoons Extra Virgin Olive Oil
  • 1  Cloves Garlic
  • 1 Tablespoons Fresh Squeezed Lemon Juice
  • 1/4 Teaspoons Sea Salt or to taste


  • 1 Cup + 1/2 Cup Gruyère Cheese – shredded and divided
  • 1 Cup + 1/4 Cup Pecorino Romano – finely shredded and divided
  • 1 1/2 lbs Yellow Potatoes – 1/8 inch slices (about 5 cups sliced) discard the ends
  • 1 lb Sliced Butternut Squash cut into 1/8 inch round slices (about 4 1/2 cups)
  • 1/2 Large White Onion – diced
  • 2 Cloves Garlic – minced
  • 1 Tablespoon Extra Virgin Olive Oil
  • 1/4 Cup Dry White Wine
  • 2 Tablespoons Salted Butter
  • 3 Tablespoons Brown Rice Flour (or regular)
  • 2 1/4  Cups Milk (I used 1% organic)
  • 1 1/2 + 1/2 Teaspoon Sea Salt – divided



Pre-heat oven to 350 degrees

Spread the hazelnuts in a single layer on a baking sheet.  Bake for 10 – 14 minutes.  In about 5 – 7 minutes stir the nuts so they toast evenly while also checking on the progress.

When hazelnuts are cool put in the center of a towel and pull corners of the towel together and roll hazelnuts around with some force till skins come loose.  A small amount of skin will remain on the nuts and that is fine.

Sometimes I separate the ones that the skins didn’t come off and put them back in the oven for a few more minutes.

 In a food processor, grind hazelnuts into a fine crumble and set aside.


 Put all the ingredient in a food processor, puree and set aside.


Mix 1 cup each of gruyère and pecorino, put in a bowl and set aside.

Mix the remaining 1/2 cup gruyère, 1/4 cup pecorino and hazelnuts together then set aside.


Slice potatoes into thin slices (about 1/8-inch thick).  Add potatoes to a pot and cover with water then bring to a boil, continue to boil for 2 minutes.  Drain potatoes in a colander, rinse with cold water.


Peel squash and cut the neck into 1/8 inch round slices, if you need more than the top of the squash provides you can use the bottom, cut in half and scoop out the seeds then thinly slice.  Lay the slices in one layer on a dish towel.  Put 1/2 teaspoon of salt in the palm of your hand and sprinkle a little on all the squash slices to remove excess water.  Let sit for at least 15 minutes.  You will amazed at how much water comes out.  Dry them with a kitchen towel or a paper towel.  Set aside.


 Mince onion and garlic, add olive oil, onion and garlic to a large heavy saucepan. Sauté over medium-low heat stirring until the onion is soft, transparent and the garlic starts to turn golden (about 10 – 12 minutes).   Add wine and reduce to a syrup.

 Add butter and salt to onions.  When butter is melted, add flour and continue stirring for about 2 minutes.

Slowly add milk a little at a time while whisking constantly. (this is important)

Bring liquid to a boil, continuing to stir then reduce to simmer.  Add cheese a little at a time, stir until the cheese is completely melted.  Add pesto mixing in completely.  Cook until sauce thickens.

Set aside 1 cup of sauce to make sure you have enough for the top two layers.


Spread a thin layer of sauce in a 2 1/2 to 3 quart casserole dish.  Layer potatoes (if you have some that are thicker than 1/8 inch place them on the outside and the thinner pieces in the middle)  then spread a thin coat of sauce over the potatoes, layer squash and repeat until the last two layers.  With the 1 cup of sauce you set aside, pour half over second to the last layer then add the last layer and pour the rest of the sauce over the top.

 Pre-heat oven to 375

 Bake uncovered 1 hour on the middle shelf.  (I put a baking sheet below to catch any juices that overflow)

 Check after 45 minutes and push down the top potato slices with a spoon to let the juices cover potatoes again.

 Mix remaining cheese and the ground hazelnuts together then sprinkle over potatoes.  Bake uncovered for 15 – 20 minutes or until top is brown and bubbly.

 Poke a knife thru the center to make sure potatoes are soft, if not bake a bit longer.  (You can put some foil on top if you don’t want it any darker on top.)

 Let slightly cool before serving.

Potato Butternut Squash Au Gratin

Health Benefits:

 Yellow Potatoes – Yukon gold’s content of potassium is higher than many foods and can help reduce the risk of hypertension and stroke. They have twice the amount of vitamin C as a Russet, which helps protects your cells from free-radical damage. Yukon’s are rich in B6 and antioxidant properties. It has a bit of Iron but the C helps the body absorb it. They contain fiber that helps reduces cholesterol, stabilizes blood sugar, helps prevent constipation and aids in weight loss,

Butternut Squash is a great source of fiber and folate making it heart and bowel healthy it has an abundance of carotenoids that is great for eye health and also helps protect against heart disease and very high levels of beta-carotene.  It regulates blood sugar levels helping to reduce the risk of type 2 diabetes and increasing energy levels.  It has a significant amounts of potassium and vitamin B6 which is great for the nervous and immune systems.  A 1-cup serving gives about half the recommended amount of antioxidant-rich vitamin C.  Winter squash also helps in the prevention of prostate, colon, lung & breast cancers.

Sage helps to enhances concentration, attention span and quickens the senses.  Its effects help deal with grief and depression.  It is useful for all types of bacterial infections.  Helps detoxify and cleanse the blood.  The herb reportedly restores color to gray or white hair.  It is also high in antioxidants. Sage is exceptionally rich source of several B-complex, it contains a very good amounts of vitamin A, beta-carotene, and C It is a rich sources of minerals like potassium, zinc, calcium, iron, manganese, copper, and magnesium *Those with epilepsy, high blood pressure, or kidney disease may be adversely affected by the thujone content and should avoid large doses of sage Other posts

Leave a Reply