Not your ordinary layered bar, carmelitas sandwich a sticky caramel, chocolate, and pecan filling between two layers of buttery, streusel-like shortbread studded with oats. Their variety of both flavors and textures make them an irresistible temptation and an easy crowd-pleaser.
Preheat the oven to 350°F with a rack in the center. Lightly grease a 9" x 13" pan and line with a parchment sling.
To make the crust: In a large bowl or the bowl of a stand mixer fitted with the flat beater attachment, combine the flour, oats, brown sugar, baking soda, and salt. Add the butter and stir with a flexible spatula by hand or on low speed of the mixer until the mixture is crumbly; stop before it comes together into a cohesive dough.
Transfer two-thirds of the crumb mixture (about 3 cups or 540g) to the prepared pan and press it evenly into the edges and corners, using the bottom of a measuring cup to pack it into a smooth layer.
Bake the crust for 10 to 15 minutes, until it's puffed slightly and is golden-brown all over.
Remove the crust from the oven and set it aside to cool for 10 minutes.
To make the caramel filling: In a medium saucepan, combine the syrup, sweetened condensed milk, brown sugar, butter, vanilla, and salt. Set over medium heat and cook for 7 to 10 minutes, stirring frequently at the beginning and constantly toward the end, until the mixture thickens and becomes pale and is bubbling vigorously around the edges of the pot and slowly burbling at the center.
Pour the caramel filling onto the crust, spreading it to the edges, and allow it to set at room temperature, about 15 minutes.
Scatter the chocolate chips and pecans evenly over the firm caramel layer, then scatter the remaining crumb mixture over top, breaking any large clumps into smaller pieces.
Bake the bars for 20 to 25 minutes, until the crust is lightly browned and the caramel is bubbling around the edges.
Remove the bars from the oven, loosen the edges, and allow them to cool completely in the pan before cutting and serving.
Storage information: Store wrapped bars at room temperature for a few days; freeze for longer storage.
For a shortcut, skip the homemade caramel filling and use our Caramel Baking Block instead. Cut the 16-ounce block into 1/2" pieces, then place it in a small saucepan or microwave-safe bowl with 2 tablespoons (28g) milk. Melt over low heat or in short bursts until smooth. Use as directed in step 7.
