Grate the russet potato using the large holes of a box grater.

Wrap the grated potatoes in a clean tea towel or cheesecloth and squeeze out as much liquid as possible into a bowl.

Let the bowl of potato water sit for 10 minutes to allow starch to settle.

Combine the grated potato and mashed potatoes in a large bowl and mix well.

Pour off the water from the bowl, leaving the potato starch at the bottom.

Add the starch to the potato mixture, then add flour, baking soda, and salt to taste.

Knead the mixture on a floured surface until a thick dough forms (1-2 minutes).

Roll the dough into a circle about 3/4 inch thick.

Cut out 3-inch rounds using a cookie cutter or glass rim.

For pan-fried boxty: Melt bacon fat or butter in a skillet over medium heat.

Fry the boxty rounds for 3-4 minutes per side, until golden brown.

For boiled boxty: Cut the dough into cakes and drop them into boiling salted water.

Cook for about 40 minutes. (Use starchy potatoes.)

Drain and cool to room temperature, then halve and fry as above.

For baked boxty: Shape the dough into a circle about 3/4 inch thick and cut into wedges.

Bake on a greased baking sheet in a preheated 300°F (150°C) oven for 45-50 minutes, turning halfway through.