In a medium saucepan, heat 1/2 the cream until simmering. Turn off the heat, add the chocolate and swirl the pan to cover the chocolate with the cream. Let sit for 3 minutes and then gently whisk until smooth. Pour into a large bowl and whisk in the remaining cream.
Cover and refrigerate until well chilled, about 3 hours or overnight. Pro Tip: Do not rush this or the ganache will not whip into peaks.
Once the milk chocolate ganache is thoroughly chilled, whip the ganache with a hand mixer or in a stand mixer with the whisk attachment on medium-low speed until medium peaks form, about 1 minute. Pro Tips: Don’t overwhip or it will get grainy when folding the ganache with the pumpkin. If you are unsure if it is done, do the final few mixes by hand to make sure it is thick enough to cling to the whisk but not stiff peaks.
In a medium bowl, stir together the pumpkin puree, pumpkin spice, vanilla, and salt. Add 1/3 of the whipped ganache and stir with a rubber spatula until mostly combined. Fold in another 1/3 of the whipped ganache until nearly combined. Gently fold in the remaining whipped ganache until no streaks remain.