Preparation Steps

• Set racks in the upper and lower thirds of the oven and preheat to 360°F (182°C). Line 3 baking sheets with parchment. In a medium bowl, whisk together flour, baking soda, and salt; set aside.
• In a large bowl, beat the softened butter, brown sugar, and granulated sugar on medium speed until creamy and slightly lightened, 2 minutes. Mix in the molasses until smooth.
• Add the egg and egg yolk and beat just until fully incorporated, scraping the bowl once. Stir in vanilla and espresso powder (if using).
• Add the dry ingredients in two additions, mixing on low only until the flour disappears. Fold in the mini chocolate chips by hand. Cover and chill the dough for 10 minutes to make scooping easier and keep the cookies tiny.
• Scoop level 1-teaspoon portions of dough and roll each into a compact ball with your fingertips. Arrange 24–30 balls per sheet, leaving about 1 1/2 inches between them.
• Bake two sheets at a time for 7–9 minutes, rotating the pans front to back and swapping racks halfway through. The edges should look set while centers remain pale and slightly puffy.
• Remove from the oven and rap the pan once on the counter to gently deflate for a classic miniature look. Cool on the sheet for 5 minutes, then transfer cookies to a rack to finish cooling. Repeat with remaining dough on a cooled baking sheet.