Step 1

Place racks in upper and lower thirds of oven; preheat to 350°. Toast almonds on a rimmed baking sheet on upper rack, tossing halfway through, until slightly darkened in color and fragrant, 6–8 minutes. Let cool.

Step 2

Gather almonds into a tight pile on a nonstick silicone baking mat or a rimmed baking sheet coated with nonstick spray. Cook granulated sugar in a small saucepan over medium heat, undisturbed, until it begins to liquefy and turn golden brown around the edges. Use a heatproof rubber spatula to incorporate melted sugar into unmelted sugar and continue to cook, stirring occasionally, until all sugar is melted and caramel turns a medium amber color, 6–8 minutes. Carefully pour caramel over almonds and let cool.

Step 3

Break almond mixture into large pieces and transfer to a food processor. Process, scraping down sides occasionally, until praline paste is very smooth and creamy (it should be as smooth as peanut butter with a slightly oily sheen; this takes time, so be patient), 12–16 minutes.

Step 4

Cook butter in a medium skillet over medium heat, swirling occasionally, until it foams, then browns, about 5 minutes. Let cool until just warm.

Step 5

Whisk flour, kosher salt, and baking soda in a medium bowl. Using an electric mixer on medium-high speed, beat brown butter, praline paste, and brown sugar in a large bowl until mixture is smooth, about 2 minutes. Reduce speed to medium, add egg yolk, vanilla, and 1 tsp. water and beat just to combine. Reduce speed to low and gradually add dry ingredients. Increase speed to medium and beat until well combined (this will help develop some gluten in the dough and help the cookies hold together). Using a wooden spoon, mix in chocolate. Scrape out dough onto a sheet of parchment paper and roll up into a 1¾"-diameter log. Chill until very firm, at least 2 hours.

Step 6

Reheat oven to 350°. Slice dough into generous ¼"-thick slices with a serrated knife (some of the chocolate pieces may fall out or get in the way—just squish them back in if they fall out; everything will meld together during baking). Place on 2 parchment-lined baking sheets, spacing 1" apart. Sprinkle with sea salt and bake until cookies are firm around the edges and slightly darker, 9–10 minutes. Let cool on baking sheets.

Step 7

Do Ahead: Praline paste can be made 1 week ahead; store airtight at room temperature. Dough can be made 3 days ahead; wrap in plastic and keep chilled, or freeze up to 1 month.