Step 1In a medium, heavy-bottomed saucepan, combine the milk and cream and bring to a simmer over medium-high heat, then reduce the heat to medium.
Step 2Meanwhile, in a small bowl, beat the egg yolks to combine. Slowly whisk about one-fourth cup of the milk mixture into the eggs to temper them, then transfer the eggs to the saucepan, whisking to combine.
Step 3Cook the custard, stirring frequently, until it is slightly thickened. Immediately add the chopped Mexican and bittersweet chocolates to the pan. Remove the pan from heat. Stir until the chocolate is melted and incorporated into the custard.
Step 4Strain the mixture into a large glass measuring cup or bowl. Ladle the chocolate into small bowls. Refrigerate the custards until set and chilled, at least 6 hours but preferably overnight.
Step 1In a medium, nonstick pan, combine the pumpkin seeds and sugar over medium-low heat. Cook, stirring frequently with a heat-resistant spatula, until the sugar is melted and coats the pumpkin seeds. Remove from heat and spread the seeds on a greased or parchment-lined baking sheet so the seeds do not stick together as they cool.
Step 1In a large bowl using a whisk or hand mixer, beat together the cream with the vanilla extract and sugar to form stiff peaks.
Step 2Serve the pots de creme with a dollop of whipped cream, a sprinkling of candied pumpkin seeds and a pinch of salt.