Dulce de Leche Sandwich Cookies

Dulce de Leche

• 1 quart full-fat organic milk
• 1/2-3/4 cup sugar (turbinado or another, less-refined sugar is preferable)
• scant 1/2 teaspoons baking soda

1. In a heavy- bottomed sauce pan with at least a 2-quart capacity, dissolve the sugar in the milk over medium-high heat.
2. Once the sugar is dissolved, stir in the baking soda.
3. Bring the milk to a near-boil, taking much care not to let it boil over. Just as it's coming to a boil, lower the heat to low and allow the mixture to simmer uncovered for 1-2 hours, stirring often (a silicone spoon or spatula is especially handy for this job). It should look like it's simmering a bit vigorously but not actually be at a full boil.
4. Remove the pan from the heat when the milk becomes a dark golden color and appears quite thick. A good test to know when it's done is to stir the mixture with a spoon and run your finger along the back of the spoon (careful-- it's hot!); the trail your finger leaves should last several seconds before slowly disappearing.
5. Allow dulce de leche to cool to room temperature.

Sugar Cookies

• 1 1/2 cup all-purpose flour, plus more for rolling out the dough
• 1/2 cup cornstarch or non-glutinous rice flour
• 1/2 teaspoon baking powder
• 1/2 cup unsalted butter at room temperature
• 1 cup granulated sugar
• 1/2 teaspoon table salt
• 1 large egg, lightly beaten at room temperature
• 2 tablespoons milk or cream
• 1 teaspoon vanilla extract

1. In a small bowl, whisk together the flours and baking powder.
2. In separate bowl, cream butter, sugar, and salt.
3. Add egg, milk, and vanilla to the sugar mixture; mix well.
4. Add dry ingredients to wet ingredients, and mix until incorporated.
5. Shape dough into a few smaller portions, flatten into discs, wrap in plastic, and refrigerate until stiff, at least one hour or overnight.
6. Heat oven to 350ºF degrees. Line cookie sheets with parchment or silicone mats.
7. Roll out dough to 1/4-inch thickness on a lightly floured surface. Cut into shapes and move to baking sheets (cookies won't spread much so they can be set quite close together).
8. Re-roll and re-cut dough scraps giving dough a bit more time in the fridge as necessary.
9. Bake cookies until lightly golden, about 10 minutes. Transfer to wire racks to cool.
10. To assemble the cookies, spread a 1/4-1/2 teaspoon of cooled dulce de leche on the flat side of the cookie and use another cookie, flat side in, to complete the sandwich.
11. Store any unused dulce de leche in an airtight container in the refrigerator.
12. Store cookies in an airtight containter at room temperature.