Gather all ingredients. Place creme eggs in the freezer and freeze until solid, at least 2 hours or up to 12 hours.

Preheat oven to 375 degrees F (190 degrees C) with rack in top third position. Line two large baking sheets with parchment paper, and set aside.

Stir together brownie mix, chocolate syrup packet, flour, butter, egg, and espresso powder (if using) in a large bowl until just combined into a stiff dough that resembles the texture of Play-Doh. Stir in chocolate chips until just combined.

Unwrap frozen creme eggs, and set aside. Portion cookie dough into 10 even portions (about 3 oz. each; about 1/4 cup packed dough). Working with 1 portion at a time, flatten dough in palm of your hand to form an even round. Place 1 frozen creme egg in center of dough round, and wrap dough to fully enclose the creme egg; place on prepared baking sheet. Repeat with remaining creme eggs and dough portions, ensuring that cookie dough balls are placed at least 2 inches apart on each baking sheet (5 per baking sheet).

Bake one baking sheet at a time in preheated oven until cookies are just set on the edges and on top, 10 to 11 minutes. Do not overbake or the creme eggs may seep out of the cookie. Let cool on baking sheet slightly, about15 minutes. Serve warm, or let cool completely on a wire rack and store in an airtight container for up to 2 days.