Creamy Squash, Potato + Cheddar Scalloped Potatoes

Ingredients

2 tbsp salted butter
3 cloves garlic, finely chopped
½ small onion, finely chopped
1 cup cream
2½ cups milk
1 tbsp flour
2 tbsp fresh sage, thyme or rosemary, chopped (or 2 tsp dried)
2½ cups sharp cheddar cheese, grated
1½ lbs (about 2-3) russet potatoes, peeled, thinly sliced
1½ lbs (about 3-4 cups) pumpkin or squash, peeled, thinly sliced
Kosher salt and freshly ground black pepper
3 tbsp Smak Dab Mustard - Curry Dijon, White Wine Herb, Honey Horseradish, Beer Chipotle, Hot and Sweet Dill or Hot Honey Jalapeño

Preheat oven to 350°F.
In a medium sauce pot, add butter and melt over medium heat. Add the garlic and onion, sauté for about 1 minute or until the onions are translucent. Add the flour and stir until combined. Slowly add the milk and cream whisking constantly so there are no lumps. Bring to a simmer for 2-3 minutes and turn off heat. Add the mustard, herbs, and season the sauce with salt and pepper.
Grease an ovenproof baking dish with butter or non-stick cooking spray. On the bottom layer spoon 1/2 cup of sauce and layer with sliced potatoes so they fan out and make a single layer overlapping by about half their size. Then pour a 1/2 cup of sauce and sprinkle about 1/2 cup of cheese. On the next layer, add the pumpkin (instead of potato), sauce, then cheese.
Repeat this layering until the dish is full. Finish the final layer with potatoes/squash and a sprinkle of cheese. Cover with foil and bake for 1 hour covered followed by 30-45 minutes uncovered, or until the sauce is thick and reduced, the surface is golden brown, and the potatoes are cooked through. Allow to cool 10-15 minutes before serving.