Grace After Meals for Pat Haba B'Kisnin

I want to eat Pat Haba B'Kisnin in the amount that requires Grace After Meals. Do I need to eat it all within the time frame of 'Achilat Pras'? And what is the ruling if there was a pause in eating during 'Achilat Pras'?

Certainly, it is not necessary to eat everything within the time frame of 'Achilat Pras', as it is not feasible, since Pras is 3, which is 162 cc, or 4 eggs, which is 216 cc, and establishing a meal on Pat Haba B'Kisnin, according to the Mishnah Berurah, requires a larger amount like an evening or morning meal, and our teacher the Rabbi explained that it is about 800 cc. Even if there was a pause and nothing was eaten in the middle of 'Achilat Pras', one still needs to recite Grace After Meals, as with bread. However, one kezayit must be eaten within 'Achilat Pras'.

Similar to the law of bread explained in Mishnah Berurah, Siman Reish, S"K 1: "But regarding bread, for satiation, its obligation is from the Torah, even if eaten little by little, it is still considered satiated." And Shaar HaTziyun wrote there, S"K 10: "But if one ate one kezayit at once, then certainly obligated by the Torah, in any case, and note:" And this means there is a doubt whether 'and you ate' from the Torah is a kezayit, and if so, it must be eaten within 'Achilat Pras', or there is no need for 'and you ate', and 'and you were satiated' suffices. And this is what Shaar HaTziyun concluded, that if one eats everything slowly, but one kezayit was eaten within 'Achilat Pras', then certainly obligated in Grace After Meals, and apparently the same applies to Pat Haba B'Kisnin, upon which a meal is established.