The narrator certainly is warning Jackson Bird, the sheep man, not to take an amorous interest in Miss Learight, who makes the pancakes. Jackson protests that he only went to see her to try to get the pancake recipe. Here, the narrator is telling him to be sure (on pain of being shot) to confine his dealings with her to pancakes. So he is saying that Jackson should stick closely to pancakes and not let his interest wander beyond that. To stick to pancakes "as close as the middle one of a stack" is a hyperbolic way of saying as closely as possible; the pancake in the middle of a stack of pancakes is as close to pancakes as it is possible to get: it has nothing but other pancakes on either side, it is as far as possible from anything that is not a pancake. The expression is nothing to do with eating a stack of pancakes.

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