Step 1

Preheat the oven to 350°. Spread the pecans on a baking sheet and toast for about 10 minutes, until golden. Leave the oven on.

Step 2

In a medium saucepan, combine both sugars with the butter and cream and cook over moderate heat, stirring occasionally, until the mixture registers 230° on a candy thermometer, about 8 minutes. Stir in the toasted pecans and salt. Cook, stirring occasionally, until the mixture reaches 240°, about 2 minutes longer. Remove the pan from the heat and stir in the vanilla. Let the mixture cool down to 210°. Stir the mixture with a wooden spoon until it stiffens and looks cloudy. Scrape the praline onto a parchment paper–lined baking sheet. Spread in an even layer and let cool. Transfer the praline to a work surface and coarsely chop.

Step 3

Meanwhile, coat a 9-by-13-inch baking pan with baking spray. In a medium bowl, sift the flour with the cocoa powder and granulated sugar. In a medium saucepan set over another saucepan of gently simmering water, melt the butter with the chocolate, stirring until smooth, about 5 minutes. Let cool slightly.

Step 4

In a large bowl, using a hand mixer, beat the eggs withthe light brown sugar and salt at medium speed for 2 minutes. Beat in the dry ingredients in 4 additions, scraping down the side and bottom of the bowl. With the mixer on, drizzle in the chocolate mixture and beat at low speed until well combined. Fold in the chopped praline.

Step 5

Scrape the brownie batter into the prepared pan and bake for about 40 minutes, until a cake tester inserted in thecenter comes out clean with just a few moist crumbs attached. Transfer to a rack to cool completely before cutting into bars.