Brigadeiro Tapioca Pancake

1/3 cup sour manioc starch (polvilho azedo)**
2 tablespoons water

Brigadeiro mole as filling — or any other filling that you desire (for a vegetarian or dairy-free version, skip this chocolate filling. You can use your favorite jam instead)

For the Chocolate Fudge Sauce:
1/2 (7 oz or 200 g) can condensed milk
1/4 cup semi-sweet chocolate chips
1 tablespoon unsalted butter, softened
1/2 tablespoon pure vanilla extract
4-6 tablespoons heavy cream
1-2 tablespoons good quality chocolate sprinkles or chocolate vermicelli (optional)