Keep 2 medium green zucchini at cool room temperature, about 70°F, for 10 minutes. Then grate them through the large holes until you have 2 packed cups. Gather the shreds in a clean towel and twist firmly for 45 to 60 seconds. Stop when about 1/3 cup liquid drains out, because pressing longer can remove too much moisture. Next, loosen the squeezed shreds with your fingers for 30 seconds. They should feel damp and fluffy rather than dripping or compacted. You’ll see pale green strands with no puddle forming beneath them. Skip this window and the brownie center can turn gummy. Squeezing removes excess water so the crumb stays dense.

Warm 4 ounces chopped 60% dark chocolate with 1/2 cup canola oil to 110°F to 115°F. Stir every 20 seconds for 1 1/2 to 2 minutes until smooth. Then whisk in light brown sugar and granulated cane sugar for 45 seconds. Add 2 large eggs and 1 1/2 teaspoons pure vanilla extract. Whisk briskly for 60 seconds. The mixture should turn thick and glossy with fine bubbles around the edge. You’ll smell warm cocoa while the sugar begins dissolving. Let it stand 2 minutes if it climbs above 120°F, because hotter chocolate can streak or tighten around the eggs. Whisking builds a stable emulsion that gives the brownies their shiny top. Preheat the oven to 350°F now so it's fully hot by the time the pan goes in.

At about 70°F, sift 1 cup all-purpose flour and 1/2 cup Dutch-process cocoa powder over the chocolate mixture. Add 1 teaspoon espresso powder and 1/2 teaspoon baking soda plus 1/2 teaspoon fine sea salt. Fold with a rubber spatula in a J-shaped motion for 20 strokes. Then add the squeezed zucchini and 3/4 cup semisweet chocolate chips. Fold 8 to 10 more times. The batter for Fudgy Chocolate Zucchini Brownies (No One Will Guess!) should look very thick and glossy. Tiny green flecks may show but no dry flour should remain. Stop within 2 minutes once the chips look evenly suspended. Go past 35 folds and the crumb can become cakey. Minimal folding limits gluten so the center stays fudgy.

Heat the oven to 350°F for at least 15 minutes. Meanwhile, brush an 8×8-inch light-colored metal baking pan with 1 teaspoon canola oil and line it with parchment. Pour in the 70°F batter and spread it to all four corners within 2 minutes. Drag the spatula in three broad passes. Then tap the pan twice so large air pockets rise without flattening every bubble. The surface should sit level with a few soft ridges and scattered chocolate chips showing. No dry patches should remain near the corners. Let the filled pan stand only 3 to 5 minutes before baking. Wait longer and the leavener starts working too early. Even spreading keeps the center and edges on the same baking schedule.

Bake at 350°F for 28 to 32 minutes. Rotate the pan 180 degrees at minute 20 and keep the oven door closed before then. Remove it when the center reaches 200°F to 205°F. A toothpick inserted 1 inch from the edge should carry several moist crumbs. Cool the pan for 60 minutes before frosting. The top should have a thin crackled skin and slightly raised edges. The center will settle as steam escapes and the chocolate smell becomes deeper. (My first batch stayed in 6 minutes longer, the edges turned dry before the center looked firm.) Go past 205°F and the dense crumb becomes crumbly. Cooling finishes the set without driving out more moisture.

Beat 4 tablespoons unsalted butter at 70°F with the remaining 1/4 cup Dutch-process cocoa powder for 45 seconds. Add 1 cup powdered cane sugar and 2 tablespoons whole milk plus 1/2 teaspoon pure vanilla extract and 1/4 teaspoon fine sea salt. Beat 2 minutes. Add the final tablespoon milk only if needed. Spread the frosting over the fully cooled slab. Let the frosting settle for 20 minutes at 68°F to 72°F. It should look glossy and hold soft swirls without running over the edges. Cut 16 uneven squares with a warm dry knife and place one square on a white plate. Frosting warm brownies makes the top slide. A cool base keeps the frosting thick and the cuts clean.