Preheat oven to 225 degrees. In a large mixing bowl, whisk together flour, granulated sugar, cocoa, baking powder, and salt. In another bowl, whisk together milk, egg, melted butter, and vanilla; pour over flour mixture, whisking to combine. Fold in chocolate chips and pecans; let batter stand until slightly thickened, 5 to 10 minutes.
In a large nonstick skillet, heat 1 tablespoon oil over medium heat until a water droplet sizzles; swirl to coat bottom of pan with oil. Reduce heat to medium-low. Spoon four small mounds (1 heaping tablespoon each) of batter into skillet. Cook until bubbles appear in center, 3 to 4 minutes. With a thin spatula, flip pancakes; continue cooking until set, 3 to 4 minutes more.
Transfer to a baking sheet; cover loosely with foil; place in oven to keep warm. Repeat with remaining oil and batter in three more batches (adjust heat as necessary to avoid overbrowning).
Stack 4 pancakes on each plate, sprinkling each layer with confectioners' sugar, if desired. Serve immediately, drizzled with hot fudge sauce, if desired.