Combine gelatin, sugar, salt, cinnamon, allspice, nutmeg, ginger, and milk in a saucepan. Whisk to blend and bloom the gelatin. Stir in the pumpkin and egg yolks. Whisk together. Cook and stir over medium heat until the mixture comes to a boil and continue on a low boil for about one minute longer. Mixture will thicken as it cooks and more so as it cools.
Remove from heat, cool to room temperature. Once cooled, chill in the refrigerator until the custard is cold and set.
Meanwhile, place the ricotta and 1 tbsp. milk or cream in the bowl of your standing mixer and beat until light and fluffy, approximately 3-4 minutes. Add maple syrup and vanilla and continue to whip until incorporated. (Ricotta does not get completely smooth like whipped cream does, so you will still have some texture to the whipped ricotta.)
Gently fold whipped ricotta into the pumpkin custard and stir until blended. Refrigerate this mixture until ready to assemble the tarts.