Creating a delicious Cranberry Mousse Pie is simple when you follow these easy steps:

1. Prepare the Cranberries: If using fresh cranberries, rinse and remove any stems. If using frozen, thaw them completely.
2. Cook the Cranberries: In a saucepan, combine cranberries and 1/2 cup of sugar. Cook over medium heat until the cranberries burst and become soft, about 10 minutes. Stir occasionally.
3. Blend the Mixture: Remove from heat and let it cool slightly. Blend the mixture until smooth, then strain it through a fine mesh sieve to remove skins and seeds. Set aside.
4. Dissolve Gelatin: In a small bowl, sprinkle gelatin over cold water. Let it sit for about 5 minutes to bloom. Then, gently heat until dissolved, being careful not to boil.
5. Mix the Mousse Base: In a large bowl, combine the cranberry puree, remaining sugar (1/2 cup), sour cream, lemon juice, and vanilla extract. Stir until well mixed.
6. Incorporate Gelatin: Add the dissolved gelatin to the cranberry mixture and stir until fully combined.
7. Whip the Cream: In another bowl, whip the heavy cream until stiff peaks form. Gently fold in the whipped cream into the cranberry mixture until no white streaks remain.
8. Fill the Crust: Pour the mousse into the prepared graham cracker crust, smoothing the top with a spatula.
9. Chill: Cover the pie with plastic wrap and refrigerate for at least 3 hours or overnight for best results.
10. Garnish and Serve: Before serving, garnish with fresh cranberries and mint, if desired.

Following these steps will lead you to a beautiful and delicious Cranberry Mousse Pie that will wow your guests!