Prepare an 8x8 baking dish by lining it with parchment paper. Set it aside.

In a food processor, process the pitted dates until coarsely chopped. Add in the puffed cereal, oats, chopped peanuts, flaxseed, cinnamon, and salt, and pulse a few times until everything is mixed together and there are no large pieces. Pour these dry ingredients into a large bowl and set aside.

In a small saucepan over low heat, or in a microwave-safe bowl, warm the peanut butter and sweetener until heated through and thoroughly combined. Remove from the heat and stir in vanilla. Pour the sweet, peanut butter mixture over the dry ingredients and stir well. It will seem dry, but that's fine.

Once all the ingredients are fully mixed, pour everything into your prepared 8x8 pan and press down firmly with your hands until the mixture is flat.

Place the pan in the refrigerator so the bars can set. Cut into 16 bars.