Line an 8x8-inch pan with parchment, leaving an overhang on two sides to lift the bars out later. Set aside.
Combine the bran cereal, ground flaxseed and dried cranberries in a large bowl. Stir briefly to distribute the flax and cranberries evenly through the cereal.
In a small saucepan over low heat, warm the SunButter and honey just until the mixture becomes fluid and glossy, stirring constantly (about 2 to 3 minutes). Remove from the heat and whisk in the vanilla.
Pour the warm SunButter mixture over the dry ingredients. Fold everything together with a sturdy spoon until the cereal is fully coated and the mixture clumps when pressed.
Reserve a tablespoon of the mini chocolate chips for the top. Stir the remaining chips into the mixture, then transfer the sticky mix to the prepared pan.
Cover the mixture with another piece of parchment or plastic wrap and press firmly using the bottom of a measuring cup or a flat spatula so the bars hold together tightly.
Sprinkle the reserved mini chips over the compacted surface and press them in gently. Chill the pan in the refrigerator for at least 45 minutes to set (you can speed it up with 20–25 minutes in the freezer if you're short on time).
Lift the parchment out of the pan, place on a cutting board, and cut into 8 bars. Store in an airtight container in the fridge for up to 1 week or freeze up to 3 months.