Instructions

1. Preheat the oven to 350F degrees.
2. Line a 9-inch-square baking dish with foil, leaving a 2-inch overhang on two sides; coat the foil with cooking spray.
3. Pulse 1 cup all-purpose and spelt flour, the diced butter, powdered sugar, 1 teaspoon vanilla, salt and cinnamon in a food processor until the mixture starts clumping together, about 1 minute.
4. Remove dough from food processor and firmly press into the bottom of the prepared pan. Bake until firm and lightly browned, about 25 to 30 minutes. Transfer to a rack and let cool 5 minutes.
5. Meanwhile, combine the dulce de leche, heavy cream, egg yolks and the remaining 1 tablespoon flour and 1 teaspoon vanilla in a medium bowl and whisk until smooth; set aside.
6. Pour the dulce de leche mixture over the crust and sprinkle with both the dark and white chocolate chips and pecans. Sprinkle with salt if using. Return bars to the oven and bake until set around the edge but slightly jiggly in the center, about 25 minutes.
7. Transfer to a cooling rack and let cool completely. Lift out of the pan using the overhanging foil. Remove the foil and cut into 20 pieces.