Preheat your oven to 350°F and lightly spray a 9x13 inch baking dish (or similar 2-quart capacity dish) with cooking spray or butter. This ensures even heating and prevents sticking. While the oven preheats, you can move forward with your mise en place.

In a large mixing bowl, whisk together the room-temperature eggs until well combined and slightly pale. Add the whole milk and whisk until fully incorporated. The room-temperature eggs will help create a smoother, more uniform custard that binds everything together beautifully. Gently fold in the crushed saltine cracker crumbs and let them soak slightly for about a minute—this helps them absorb the milk and creates a silkier texture throughout the casserole.

Add the drained corn, minced onion, sugar, salt, and freshly ground black pepper to the custard mixture from Step 2. Cut the butter into small pats and scatter them throughout the mixture as you stir—don't fully incorporate the butter; small pieces will melt throughout the casserole during baking and create pockets of richness. I like using good-quality salted butter like Kerrygold because it adds a subtle flavor dimension that elevates the whole dish. Stir everything gently until just combined, being careful not to overmix, which can make the casserole tough.

Pour the complete casserole mixture from Step 3 into your prepared baking dish, spreading it evenly. Bake uncovered at 350°F for 40 minutes until the top is set and lightly golden, and a knife inserted near the center comes out clean or with just a few moist crumbs. The casserole will continue to firm up slightly as it cools.