For the bar topping and base
1½ cups all-purpose flour
¼ teaspoon salt
¾ teaspoon baking soda
1 cup firmly packed dark brown sugar
1¾ cups rolled oats
1 cup (2 sticks) unsalted butter, melted
1 cup toasted pecans, chopped into large pieces
1 cup chocolate chips
For the caramel filling
¾ cup firmly packed light brown sugar
1 cup (2 sticks) unsalted butter, cut into cubes
3 tablespoons heavy cream
Pinch of salt
Make the bar topping and base
Preheat the oven to 350ºF. Line a 9-by13-inch light-colored metal baking pan with foil. Butter the foil. In a medium bowl, whisk together the flour, salt and baking soda. Use your fingers to rub in the brown sugar. Add the oats and stir until the ingredients are evenly combined. Make a well in the center of the dry ingredients, then pour in the melted butter and stir until the entire mixture is wet and combined.
Spread two-thirds of the mixture across the bottom of the prepared pan and bake for about 12 minutes, or until lightly golden around the edges. Remove the pan from the oven to cool (but leave the oven on). Sprinkle the pecans and the chocolate chips across the cooled crust.
Make the caramel filling
In a medium saucepan over medium-high heat, melt the sugar and butter together. Bring the mixture to a boil and boil for 1 minute, stirring constantly (the caramel will begin to darken quickly at this point.) Remove the pan from the heat, stir in the cream, and pour the caramel directly over the chocolate pecan layer. Use an offset spatula to evenly distribute the caramel. Sprinkle the remaining oatmeal mixture onto the caramel and bake for 10 to 12 minutes, or until the top is golden brown.
Let the bars cool in the pan for about 15 minutes, then place the pan in the refrigerator and chill for 1 hour to firm up. Cut and serve. The bars can be stored, tightly wrapped, in the refrigerator or at room temperature for up to 3 days.