Soufflé has been given a bad rap as being fussy and difficult to get right. Nonsense. With just a little attention and preparedness for when it comes out of the oven, anyone can succeed at serving this puffed, cheesy crab soufflé without a hitch.
Arrange an oven rack on the lowest position and preheat oven to 375°F. Butter a 1.5-quart (48-oz, 7-inch) souffle dish and coat the inside with 2 tablespoons grated parmesan, tapping out excess. Chill in fridge until ready.
Melt butter in a medium saucepan over medium heat. Add flour and whisk until bubbly, about 1 minute. Add milk a little bit at a time, whisking smooth after each addition, until all of the milk has been added. Bring to a boil and reduce to a gentle simmer, whisking to prevent scorching.
Season with ¼ teaspoon salt and ¼ teaspoon black pepper and cook, whisking often, until sauce is thick and has lost the raw flour taste, about 5 minutes.
Transfer to a bowl and let cool slightly. Whisk in Dijon and then the egg yolks, one at a time, until well mixed. Fold in crab meat and herbs. Set aside.
Use a stand mixer fitted with a whisk attachment to beat egg whites and cream of tartar on medium speed until loose and foamy, about 3 minutes. Increase speed to medium-high and beat until peaks are stiff, being careful not to over beat.
Stir ⅓ of the egg whites into the base to lighten. Mix in the white Cheddar and the remaining 2 Tablespoons Parmesan. Gently fold in the rest of the egg whites, stopping when a few streaks are still visible.
Pour the soufflé mixture into the prepared dish and spread the top smooth.
Bake until top is golden brown and soufflé has risen, 35-40 minutes. Serve at once.