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very easy
Prep Time
10 mins
Total Time
2 h
10 to 12


¼ cup
unsalted butter, divided
60 mL
cloves garlic, minced
1 tbsp
finely chopped fresh thyme, plus sprigs for garnish
15 mL
3 tbsp
all-purpose flour
45 mL
2 ½ cups
625 mL
⅔ cup
finely grated Parmesan cheese, divided
175 mL
2 tbsp
Dijon mustard
30 mL
1 tsp
5 mL
½ tsp
2 mL
4 lb
yellow-fleshed potatoes, peeled and thinly sliced
2 kg
large onion, thinly sliced


Step 1

Preheat oven to 190°C (375°F). Grease 9 x 13-in. (3-L) baking dish. Melt 3 tbsp (45 mL) butter in saucepan over medium heat. Add garlic and thyme; cook 1 to 2 min. until softened. Sprinkle in flour. Cook, stirring, 2 to 3 min. until flour absorbs butter. Gradually whisk in milk until smooth. Continue whisking sauce while bringing just to a boil. Reduce heat to medium-low. Cook 6 to 7 min. until slightly thickened. Remove from heat. Stir in half the cheese, plus the mustard, salt and pepper.

Step 2

Layer half the potato slices and half the sliced onions in baking dish. Pour half the sauce evenly over top. Layer with remaining onions and potatoes, being sure to end with potatoes on top. Pour remaining sauce over top. Sprinkle with remaining cheese and dot with remaining butter. Arrange sprigs of thyme over top. Cover tightly with foil; place baking dish on baking sheet.

Step 3

Bake 1 hr. Remove foil. Bake additional 30 min. until potatoes are tender and top is golden brown. Let stand 10 min. before serving.


Add a pinch of nutmeg to the cream sauce as it cooks for a hint of extra flavour.

Disclaimer: We seek to be accurate with respect to the ingredients, nutritional information, product images and descriptions listed on our website, however, this information may change from time to time. Please always refer to the product package for the most current and accurate ingredient and nutrition information or other product information.

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Nutrition Facts

Nutrition Description:
Per serving (1/12 recipe):
7 g
Saturated Fat:
4 g
29 g
2 g
3 g
20 mg
8 g
390 mg
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