Whisk the sugar, cocoa powder, cornstarch and salt together in a saucepan until no lumps remain.
Gradually whisk in the coconut milk and almond milk until smooth, then cook over medium heat, whisking constantly, until the mixture simmers and thickens, about 3-5 minutes.
Remove from the heat and stir in the chopped chocolate and vanilla until completely melted and glossy.
Let the mixture cool for 15 minutes, then pour into popsicle molds and insert the sticks.
Freeze for at least 6 hours until solid.
Dip the molds in warm water for 10-15 seconds to release the fudge pops easily.