Fudgy Brownie Cake

1 Generously grease the inside of the slow cooker canister by holding a small slice of butter with a paper towel and rubbing the butter all over the surfaces.

Add some flour, then turn the crock this way and that to coat both the bottom and the walls with a fine, even dusting. Tap out any excess flour.

2 Set up a double boiler with about 1 inch of water in the bottom pan, simmering over medium heat—or place a large, heat-safe metal bowl over a medium saucepan with a similar amount of simmering water.

Add the butter and both chocolates. Stir with a rubber spatula until about two-thirds of the chocolate has melted.

Remove the top half of the double boiler or the bowl from the saucepan below, then continue stirring off the heat until all the chocolate has melted. Cool for 10 minutes.

3 Meanwhile, beat the sugar, eggs, and vanilla in a large bowl with an electric mixer at medium speed until quite thick and pale yellow, up to 10 minutes.

4 Beat in the cooled chocolate mixture until smooth, then scrape down and remove the beaters. Fold in the flour and salt with a rubber spatula, using wide, gentle arcs to make sure every speck of flour has been moistened.

Pour and spread this mixture into the slow cooker.

Lay long strips of paper towels across the top of the slow cooker, overlapping each other and hanging down the sides for stability. Set the lid in place, then cook on high for about 1 hour 20 minutes in a small (2- to 3 1/2-quart) slow cooker, about 1 hour 40 minutes in a medium (4- to 5 1/2-quart) one, or about 2 hours in a large (6- to 8-quart) model, or until the cake is firm to the touch and the edges are dry while the middle is dark and moist. Unplug, uncover, and cool in the canister for 30 minutes before cutting out slices with a nonstick-safe knife or setting a cutting board over the cooker, inverting it, and turning the cake out.

Ingredients for a 2- to 3 1/2-quart slow cooker:6 tablespoons (3/4 stick) unsalted butter, cut into small bits, plus more for greasing the canister6 1/2 ounces dark chocolate, chopped1 1/2 ounces unsweetened chocolate, chopped3/4 cup sugar1 whole large egg, plus 1 large egg yolk, at room temperature1/2 tablespoon vanilla extract1/2 cup all-purpose flour, plus more for coating the canister1/4 teaspoon salt

Ingredients for a 6- to 8-quart slow cooker:12 tablespoons (1 1/2 sticks) unsalted butter, cut into small bits, plus more for greasing the canister13 ounces dark chocolate, chopped3 ounces unsweetened chocolate, chopped1 1/2 cups sugar3 large eggs, at room temperature1 tablespoon vanilla extract1 cup all-purpose flour, plus more for coating the canister1 teaspoon saltTESTERS' NOTES• Because of the way the slow cooker traps moisture inside, brownies come out fudgy, dense, and moist. The edges, however, will dry out a bit—and be a boon to those who like cakey brownies. • When you're melting chocolate over a double boiler, control the heat so the water below barely simmers. Too much steam can condense into the chocolate, causing it to seize—that is, break into threads and a thin liquid. If the chocolate seizes, there may be no help for it. Try stirring in a little cream to see if the mixture will cohere. You may have to start over, even with the best of intentions. • Room-temperature eggs stabilize batters, building structure in tiny air pockets that create that vaunted crumb, the hallmark of good baked fare. To bring eggs to room temperature, leave them on the counter (but still in their shells) for 20 minutes, or immerse them (again, still in their shells) in a bowl of warm (not hot) tap water for 3 to 4 minutes. • We also like these with a little kick from up to 1/2 teaspoon cayenne added with the salt. SHORTCUTS Omit greasing and flouring the slow cooker and instead use baking spray, a mix of oil and flour. INGREDIENTS EXPLAINED Good-quality chocolate is most often sold with a percentage on the label—55 percent, 60 percent, 70 percent, and so on. The number refers to the percent of cocoa solids (the bitter chocolate stuff) as opposed to the sugar, cocoa butter, and certain stabilizers. As a general rule for this book, 40 to 55 percent is semisweet chocolate, 60 to 65 percent is bittersweet, and 70 to 85 percent is dark chocolate. Milk chocolate is just that: chocolate with milk added to the mix. And unsweetened chocolate, sometimes called baking chocolate, has no (or in some brands, very little) sugar in the mix. ALL-AMERICAN KNOW-HOW For the best baked goods, beat and beat and beat the sugar and eggs. The more air you add, the more loft you'll get. Yes, you can beat in so much air that the cake will not hold together when cut; but in general, beat until you think you've got a smooth, thick mixture—then beat it some more. However, once you add the flour, stop beating altogether. Fold the flour mixture into most batters with a rubber spatula (yes, there are exceptions). Beating will elongate the flour's glutens, resulting in tough, chewy cakes. Folding will hold off said elongation. Don't overdo even the folding: work just until you see no more dry pockets. Some graininess from moistened but undissolved flour is expected—and encouraged.