Blueberry Jam Sandwich Cookies

Ingredients

• 2.3 cups flour 
• 12 ounces blueberries fresh
• 2 large egg yolk 
• 3 tablespoons lemon zest finely grated
• 2 tablespoons premium fruit pectin 
• 24 servings sugar raw (for sprinkling)
• 0.3 teaspoon salt 
• 1 cup sugar 
• 1 cup butter unsalted room temperature (2 sticks)

Equipment

• bowl
• frying pan
• baking sheet
• baking paper
• oven
• hand mixer

Directions

1. Combine blueberries, fruit pectin,and butter in large nonstick skillet. Stirconstantly over medium-high heat untilmixture boils.
2. Add sugar and return toboil, stirring until sugar dissolves. Boiluntil mixture is reduced to 1 1/3 cups, about5 minutes.
3. Remove from heat.
4. Transfermixture to small glass bowl; cover and chilluntil jam is cold, at least 6 hours (jam willthicken slightly while chilling). DO AHEAD: Can be made 1 week ahead. Keep chilled.
5. Using electric mixer, beatbutter, 1 cup sugar, lemon peel, and saltin large bowl until light and fluffy, about 2minutes.
6. Add yolks and beat until blended.
7. Add flour in 2 additions, beating just untilblended after each addition. Gather doughtogether; divide in half.
8. Place 1 dough halfon sheet of waxed paper or parchment paper.Form dough into 1 1/2-inch-wide square orround log; smooth with dampened fingers.Wrap log in waxed paper. Repeat withsecond dough half. Chill dough until firm, atleast 4 hours. DO AHEAD: Can be made 1 dayahead. Keep chilled.
9. Position rack in center of oven andpreheat to 400°F. Line 2 large rimmed bakingsheets with silicone baking mats, smoothside up, or parchment paper.
10. Cut dough logsinto scant 1/4-inch-thick squares or rounds.Arrange on prepared baking sheets, spacing2 inches apart.
11. Sprinkle half of doughsquares or rounds generously with rawsugar (leave remaining plain).
12. Bake cookies, 1 sheet at a time, untiledges are light golden, 10 to 12 minutes.
13. Transfer cookies to rack and cool completely.DO AHEAD: Can be made 3 days ahead. Storeairtight at room temperature.
14. Just before serving, spread 1 generousteaspoon jam over bottom (flat side) of eachplain (not sugared) cookie. Top each withsugared cookie, sugared side up, and serve.
15. * Also called turbinado or demerara sugar;available at most supermarkets and atnatural foods stores.
16. Powdered fruit pectincan be found in the baking aisle at manysupermarkets.