In the food processor, pulse the all-purpose flour and salt to combine.

Add the cold butter cubes and continue pulsing until coarse crumbs form.

Add the ice cold water and continue pulsing until a dough ball forms.

Flatten the dough ball into a disc and wrap in plastic wrap. Chill at least 30 minutes.

When the dough has chilled, roll it out onto a lightly floured surface until it's approximately 2" larger in circumference than the tart pan.

Lightly roll the dough around the rolling pin and carefully transfer it to a tart pan that has been liberally sprayed with baking spray.

Gently unroll the dough from the rolling pin over the tart pan.

Carefully press the dough into the corners of the pan, and up the sides.

Use light pressure to press the rolling pin over the top of the tart pan to trim off the excess dough.

Place the tart pan on a parchment paper (optional) baking sheet and chill for approximately 20 minutes.

Once chilled, dock the bottom of the pie crust with the tines of a fork, or line the inside of the tart dough with parchment paper and pie weights (this will prevent the crust from bubbling).

Bake in a preheated 400 degree oven for 10 minutes. Remove the pie weights (if using) and continue baking for an additional 5-7 minutes.

Pierce and microwave the potatoes until cooked through. Set the cooked potatoes aside to cool.

In a large skillet, cook the cut bacon until nearly crisp. Drain the fat if desired.

Cut the cooled potatoes into chunks and add them, along with the chopped onion and 1 tablespoon butter, into the skillet with the bacon.

Continue cooking, stirring occasionally, over medium heat until the onions are translucent (approximately 5 minutes).

Season the potato/bacon mixture with salt and pepper to taste.

Add the potato and bacon mixture evenly into the par-baked tart shell.

In a small bowl, whisk together the eggs, milk, mustard, ½ teaspoon salt and ¼ teaspoon pepper.

Pour the egg mixture evenly into the tart pan and top the entire tart evenly with the crumbled Dubliner cheese.

Bake the tart in a preheated 375 degree oven for 50-60 minutes until filling is set and firm to the touch.

Cool on a cooling rack for 15 minutes and then remove the outer ring from the tart pan (if using), and allow the tart to cool for an additional 10 minutes before cutting into wedges and serving.