Preheat oven to 375 degrees F. Butter or spray a 13x9 pan and line with parchment paper, so that paper extends over the long side of the pan.
In a large mixing bowl, combine oats, flour, brown sugar, baking soda, and salt. Stir until evenly combined. Add melted butter and stir with a wooden spoon (or use your hands if the butter is cool enough) until the mixture is crumbly. Set aside 2 cups of oat mixture. Press remaining oat mixture into prepared pan. Bake crust for 10 minutes. Remove and allow to cool. Lower oven temperature to 350 degrees.
Put half (100g) of the dark chocolate in a microwave safe bowl and heat in 15 second intervals until just melted. Stir in the sweetened condensed milk until well combined. Pour the chocolate-condensed milk mixture over the cooked crust.
Add the remaining dark chocolate (100g) and raspberries to the uncooked oat mixture. Sprinkle over the top of the bars. Bake until golden brown, 28-30 minutes. Cool completely and refrigerate before cutting into squares.