Who wrote the book of love? The answer’s obvious: Dawn Casale and David Crofton, husband-wife owners of One Girl Cookies in Cobble Hill.Their new cookbook is chockful of the recipes we’ve swooned over since the day the bakery opened in 2005. Here’s a sweet preview.Banana Whoopie PiesMakes 24Ingredients1 lb. ripe bananas½ tsp. fresh lemon juice4 c. all-purpose flour1½ tsp. baking powder½ tsp. baking soda1½ tsp. table salt1 c. canola oil3 lg. eggs1 c. granulated sugar1 c. light brown sugar, packed 1 tsp. vanilla extractDulce de leche filling (recipe below)1. In a food processor, combine bananas and lemon juice; puree.2. In a medium bowl, whisk together flour, baking powder, baking soda, and salt.3. In the bowl of an electric mixer fitted with the paddle attachment, beat together oil, eggs, sugars, and vanilla on medium speed for 2 minutes. Scrape down the sides of the bowl with a rubber spatula. Add banana puree and mix on low for 30 seconds.4. Scrape down the bowl again. With mixer on low, gradually add flour mixture for 30 seconds. Carefully scrape down the bowl again. Refrigerate batter for 30 minutes.5. Preheat oven to 350°. Line a baking sheet with parchment paper.6. Using a pastry bag fitted with a large plain tip (the hole should be about as large as the tip of your ring finger), pipe 2-inch-diameter circles onto the prepared baking sheet, leaving 1½ inches between them. (Be careful to keep your pastry bag completely vertical to achieve nice circles. If you have to wait between batches, keep the batter refrigerated.)7. Immediately, put them in the oven. Bake for 10 minutes without rotating the sheet. They are done when they are slightly golden in color and spring back when touched. Remove and let cool completely.8. To fill the whoopies, turn half of them over. Using a pastry bag, pipe a dollop of dulce de leche filling onto each whoopie bottom. Top with remaining whoopies.Dulce de Leche Filling Makes two cupsIngredients4 oz. packaged cream cheese, at room temperature5 tbsp. unsalted butter, at room temperature1 tsp. vanilla extract¼ tsp. salt1/3 c. dulce de leche (available in the specialty section of the supermarket)3 c. confectioners’ sugar, plus more if needed1. In the bowl of an electric mixer fitted with the paddle attachment, beat together cream cheese and butter on medium speed until mixture is light and fluffy (about 3 minutes). Scrape down the sides of the bowl with a rubber spatula.2. Add vanilla, salt, and dulce de leche; mix for 30 seconds on low. With the mixer still on low, gradually add confectioners’ sugar; beat for 1 minute. Scrape down the bowl.3. If the filling is too soft to hold its shape, add more confectioners’ sugar, 1 tbsp. at a time, until you reach the desired consistency.4. Store in the refrigerator with plastic wrap pressed onto the surface of the filling in an airtight container for up to 5 days.One Girl Cookies is available online at onegirlcookies.com, $22.50. Book signing and tasting, tomorrow, 7 p.m., at BookCourt, 163 Court Street, between Dean and Pacific Streets, Cobble Hill (718-875-3677 or bookcourt.org); January 18, 7 p.m., at The PowerHouse Arena, 37 Main Street, at Water Street, Dumbo (718-666-3049 or powerhousearena.com).Photo: Iain Bagwell; Recipe: Reprinted from One Girl Cookies, by Dawn Casale and David Crofton, copyright 2012.