Spray a small square pan (I used a 8x8 pan) with neutral oil spray, or brush with oil if you don't have spray. You can also line with parchment paper if you are worried about the fudge sticking, however oil was enough for me.

Add condensed milk to a small saucepan, and heat on low while stirring constantly. Fold in chocolate or carob chips, while continuing to stir gently.

When chips are fully melted and combined with condensed milk, fold in the walnuts and vanilla.

Pour into the pan, and smooth the mixture with a spatula or jiggle the pan to even it out.

Refrigerate for at least one hour to set. Flip pan over onto a clean surface, or lift out by parchment paper. Cut into squares, and serve immediately or keep refrigerated until ready to serve.