Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

Cream together the softened unsalted butter, brown sugar, and granulated sugar using an electric mixer for about 1-2 minutes.

Add in the two whole eggs, one additional yolk, and vanilla extract. Mix until smooth.

Gradually add the self-rising flour to the mixture, mixing gently until just combined.

Spread two-thirds of the dough evenly in the greased baking dish.

Whisk the grape jelly until smooth and pour over the dough base evenly.

Drop the remaining dough in dollops over the jelly layer.

Bake for 30-40 minutes until the edges are golden brown.

Allow the bars to cool in the pan for 15 minutes then slice into squares.