Soak almonds in warm water for about 2 hours. Remove the skins and pulse in a food processor until almonds grind to powder but not into a paste.
Peel the skin from butternut squash and cut into half lengthwise. Remove the pulp and finely grate using a mandoline or other grater. You should have 3 cups tightly packed shredded squash.
Meanwhile prepare milk-sugar syrup: place milk and sugar in a large heavy pot or Dutch oven. Cook the mixture until is gets thick and is reduced to about one fourth of the original quantity (30-45 minutes).
Take the cardamom pods, remove the skins and grind the seeds into a fine powder with your mortar and pestle.
In a large, wide bottomed pot, heat ghee on medium heat.
Add the grated butternut squash to the melted ghee. With a big slotted spoon, gently mix and cook the squash for about 20 minutes, stirring frequently, until the raw smell of squash disappears and color changes from yellow to orange-yellow.
Add the ground almonds and condensed milk-sugar syrup, cardamom powder and rose water. Gently mix and stir constantly until the mixture comes together in a solid mass (10-15 minutes).
Remove the halwa from heat and spread the mixture into a baking dish, allowing it to cool. Place dish, covered, into freezer for another hour to allow additional firming. Remove pan from freezer and cut halwa into small squares.
Serve chilled, or store up to one week, refrigerated.