Can cheese in hand luggage be mistaken for plastic explosive?

They can easily test for plastic explosives, so that is probably not an issue, but you may still be denied bringing it in your hand luggage. I have several times, flying from different airports in Europe, been refused bringing 'creamy' foods in my hand luggage. It is obviously disputable where the border between liquids and solid substances are drawn by the security agents.

The best list of liquids under the EU directives I am aware of is curiously on the Debrecen airport security page (why does such a small airport provide such a detailed list when seemingly noone else does?):

All drinks (including beverages, water, soup, syrups), chocolate creams, creams, oil, cheese spread, liver cream, pastas, peanut butter, yogurts, cottage cheese, butter, margarine, frozen food, tins, liver wurst, sausage, jelly, mousse, hair colorants, mascara, fluid lipsticks, fluid masks, lotions, spray and roll-on deodorants, perfumes, nail polish removers, and all items made of similar substances.

I can't see how soft cheese could pass if liver wurst and sausage can't.

You describe the cheese as needing to be opened from the top to avoid spilling it. This will be especially the case when it's in your luggage and not being refrigerated. As such, the cheese will absolutely be counted as a "liquid or gel", which is prohibited in hand luggage unless it's in a container of under 100ml and in a one-litre resealable plastic bag.

The only way you will get your cheese through security is if they assume it's solid based on the outside appearance. However, in the comments, you say that the cheese is well-known in the country you're flying from, so it's unlikely that they won't recognize it.

Of course they know that, if it really is cheese, it's completely safe. However, the job of the people doing the security checks is to implement the rules, and the rules say that liquids and gels can only be carried under certain conditions.

I have seen cheese confiscated at security multiple times this year in Belgrade's Nikola Tesla Airport (BEG). Among these was completely solid cheese. However, all these cases involved larger amounts (> 1kg).

To avoid problems with it being a borderline solid, the night before flying drop the cheese in the freezer. When you go, wrap it in a towel to keep it cold.