Can butter mayonnaise stay soft when it cools?

Melted butter and eggs can make a sauce, but the home cooks in this cooking discussion mostly compared an all-butter version to hollandaise rather than ordinary mayonnaise. They cautioned that it may firm up as it cools; half butter and half oil was suggested as an experiment, but no result was reported.

Is a butter-and-egg sauce still mayonnaise?

Hollandaise was the comparison that came up most often when cooks considered replacing mayonnaise’s oil with butter. That gives a useful direction for the question, but the replies did not settle on a single name for the proposed sauce.

Some commenters treated the preparations as closely related, especially when using an immersion blender. Others emphasized differences in ingredients, proportions, and whether the egg is cooked. The discussion therefore supports thinking of hollandaise as the closest comparison, not declaring that every butter-based version must fit one particular name.

Will the butter firm up as it cools?

The main caution was texture. Multiple home cooks warned that a butter-based sauce could firm up when cold, and some advised using it warm or right away. An all-butter version should not be assumed to behave like ordinary mayonnaise in the refrigerator.

The replies did not agree on exactly how firm the sauce would become or how temperature would affect every version. More importantly, nobody reported a completed test of the proposed butter mayonnaise. That leaves the final refrigerated texture unresolved, rather than confirming either a soft sauce or a solid one.

Advice to use it warm or promptly was a practical suggestion from the discussion, not a tested storage guideline. The thread does not establish a refrigerator shelf life for this version.

What butter-and-oil proportion could you try?

The suggested compromise was half butter and half oil. It was offered as something to try if an all-butter sauce became too firm, not as a demonstrated way to prevent firming. For cooks considering recipe substitutions, this particular swap remains an experiment rather than a confirmed replacement.

• Half butter and half oil: proposed as a compromise, with no reported test result.
• Half neutral oil and half butter with two eggs instead of one: one commenter’s more specific suggestion, not a complete recipe.
• A higher egg ratio: suggested by one commenter to help the sauce stay softer in the refrigerator, but not confirmed by a reported result.

These suggestions should remain separate from an established method. The discussion gives possible proportions to explore, but it does not supply a verified ingredient list and preparation sequence for them.

Would an immersion blender work?

More than one commenter said the immersion-blender techniques for mayonnaise and hollandaise are similar. That makes the tool relevant to the question, but similarity in blending technique does not establish that the ingredients can be exchanged without changing the proportions.

One commenter described mayonnaise as one egg per cup of oil and hollandaise as four eggs per cup of butter. Those numbers were an individual comparison, not a verified recipe. They illustrate the ratio difference that some commenters emphasized, without providing enough information to turn the discussion into step-by-step instructions.

The distinction matters here: agreement about using a blender was stronger than agreement about treating the two sauces as interchangeable. No tested immersion-blender method for the proposed substitution was reported.

What should you try first?

Start by treating an all-butter sauce as closer to hollandaise, with the expectation that cooling may change its texture. The strongest advice favors using it warm or right away rather than counting on a soft refrigerated result. If you try half butter and half oil, keep its untested status in mind.