Step 1

Preheat oven to 425F.

Step 2

Scrub the potatoes and attach them to the spiralizer to be thinly cut into slices. Alternatively, cut them thinly (2 mm) with a knife or a mandoline.

Step 3

Rinse the potatoes to wash away some of the starch and then dry them well. Toss the potatoes in olive oil and salt and arrange them on their edges, standing up in the rows in a casserole dish. Slip garlic slices in between every couple pieces of potato.

Step 4

Bake for 30 minutes.

Step 5

Add the milk and cream to the casserole dish.

Step 6

Bake for 20 minutes more, or until the potatoes are tender.

Step 7

Carefully spread out the potato slices a little and slip cheese, prosciutto, sage, and rosemary in between. So long as I was quick, I could use my fingers; however, a utensil such as a spoon or butter knife would work as well. Don't worry about being too neat about it. Sprinkle some in between the rows, some in between the slices, and the rest over the top.

Step 8

Bake the gratin for 10-15 minutes, or until the cheese is melted and the prosciutto is a little crispy.