-
1
Preheat the oven to 400 F.
-
2
Place a baking sheet in the oven to heat for 5 minutes.
-
3
In a large bowl, toss together the yam dice, olive oil, 1 teaspoon of the salt, and 1/2 teaspoon of the pepper.
-
4
Pour onto the hot baking sheet.
-
5
Bake for 20 minutes, or until the yams are brown and cooked through.
-
6
Remove from the oven, transfer the yams to a medium bowl, and mash them.
-
7
Set aside.
-
8
While the yams are roasting, peel half or all of the peel from the potatoes.
-
9
(Leaving some of the peel on adds texture and color to the dish.)
-
10
Cut the potatoes into 2-inch pieces.
-
11
Put the potatoes in a large pot and cover them with cold water.
-
12
Add 1 teaspoon of the salt, bring to a boil, and boil for 20 to 25 minutes, or until the potatoes are just cooked through.
-
13
In a small pot, heat the milk over low heat.
-
14
Strain the potatoes and return them to the pot.
-
15
Add the butter, remaining salt and pepper, both cheeses, and the garlic powder, thyme, and warm milk.
-
16
With a potato masher, gently mash the potato mixture.
-
17
The potatoes should be slightly chunky.
-
18
Gently fold in the roasted yams with the masher or a spatula.
-
19
Do not fully incorporate the yams; leave spikes of color throughout the potatoes.
-
20
Serve warm.
-
21
The potatoes will keep, covered, for up to 5 days in the refrigerator.
-
22
Reheat, covered, in a 350F.
-
23
oven for 30 minutes.
-
24
Add more milk if needed.
