The phrase "potato mash" refers to mashed potatoes, which are potatoes that have been cooked, softened, and then mashed until they become a smooth and creamy texture. Full definition
For example, I sometimes serve roasted sweet potatoes mashed with a little butter, brown sugar, cinnamon and orange zest. (thelunchtray.com)
My mother in law is Mexican and she makes these as simple as they come (potatoes mashed with butter and salt, spread in the tortilla first and then fried). (thecandidappetite.com)
Grilled fish with steamed vegetables, small portion of home - made potato mash (use milk only, no butter). (womenshealthandfitness.com.au)