Browned butter

I read in Gourmet Magazine about using browned butter in cookies so I tried substituting browned butter in a recipe and sandwiched the cookies with some dark chocolate. The cookies are really crumbly and delicate at first, but surprisingly, firm up in a couple of days. Yummy with a cup of tea.

Chocolate sandwich cookies

2 sticks (1 cup) cold unsalted butter, cut into pieces
2/3 cup sugar
1/8 teaspoon salt, slightly rounded
1 large egg yolk
2 teaspoons vanilla
2 1/3 cups all-purpose flour
1 teaspoon baking soda

8 oz. dark chocolate

Melt butter in a heavy saucepan over medium heat and cook, stirring occasionally, until butter turns golden with a nutlike fragrance and flecks on bottom of pan turn a rich caramel brown, 10 to 15 minutes. Place pan in ice water bath to stop cooking, and cool, stirring frequently, until butter starts to look opaque, 4-5 minutes. Remove pan from sink and transfer cooled browned butter to mixing bowl. Add sugar and cream until light and fluffy. Beat in egg yolk and vanilla.

Combine flour, baking soda, and salt in a small bowl and stir into butter mixture until a dough forms. Turn cookie dough onto a sheet of plastic wrap and shape into a log 1 ½ inch diameter. Refrigerate for 1 to 2 hours (to firm up dough and allow flavor to develop).

Form and bake cookies:

Put oven rack in middle position and preheat oven to 350°F.

Unwrap log and slice into scant ¼ inch cookies. Place each cookie flat side down on an ungreased baking sheet. Bake cookies until just pale golden, 10-12 minutes. Cool cookies on sheet on a rack 5 minutes, then carefully transfer cookies to rack and cool completely, about 30 minutes. Cookies are very delicate and require gentle handling.

After cookies are cool, heat chocolate in a small bowl in microwave 30 seconds at a time, checking until edges start to melt. Remove and stir until melted.

Spread the flat side of a cookie with a thin layer of chocolate. Sandwich with flat side of another cookie. Continue with remaining cookies and chocolate, then let stand until set, about 45 minutes. Transfer cookies to an airtight container and wait 2 days before eating.