Liquid made with cream and penicillium roqueforti?

I honestly doubt that growing blue mould in cream for a few days will have much effect, but why not try, it won't harm you either.

Why is it not going to work? Mould needs oxygen to grow. When making blue cheese (or generally cheese with "internal" mould), holes are punched through the curd to create air channels to supply the mould with oxygen. A Wikipedia image of Gorgonzola clearly shows how the mould grows around one of these punch holes. You can also see how the mould only grows around other natural cracks in the curd, while there are large solid areas of cheese with no visible sign of mould at all.

If you don't do this and the curd is without naturals cracks, the mould will only grow on the cheese surface, like for example on a Camembert.

If you soak a piece of blue cheese in cream, some spores may of course dissolve and reach the surface, but they will only be able to grow on the cream's surface. Another problem is that Penicillium roqueforti is not growing particularly fast. Roquefort is for example ripened at least four months under ideal conditions, so just a few days will not allow much growth.

Why is it not going to harm you? Using harmless or perhaps even beneficial moulds like Penicillium roqueforti to prepare food is not only done for the taste, but also for their preserving functions. Or more precisely, different species of mould tend to fight each other, so seeding food with a "good" mould will prevent the growth of "bad" mould. Anyway, cream will get sour and taste bad long before dangerous amounts of mould would grow.

The name -

There are hundreds and thousands of penicillia moulds which exist in the world. Mostly, they grow to form green colonies.

The ones which are used to give flavour to cheese generally grow to give blue colonies when cultured.

Those which grow under culture to give blue colonies with white edges are not useful for antibiotic production or flavour properties.

The name? The moulds that work only have names because they have been used to produce commercial products. Those which produce blue colonies are often used for cheese making. They are named because people use the moulds habitually for cheese production - pick your name with your cheese.

I said above that the penicillium is usually trying to indicate by producing an "off-flavour" that the food material is no longer edible for humans. It is not generally the truth that the food is inedible - the flavour is only a deflection tactic, the food is still edible. Within cheese the flavour is usually introduced from a known mould of traditional origin.

Safety concerns - if the "starter culture" comes from an acknowledged safe source, an approved food cheese, you're down to considering the possibilities from associated organisms, like Listeria. You need to think about controlling the "external aspects" of the preparation.

When mould grows on your food, it often gives the food a flavour you don't like.

Mostly, that flavour is making a statement. The mould is saying "this is my food, not yours". You could eat it, despite the "off flavour" - but people avoid taking chances -if it comes down to "can I eat this and live happily", they are mostly wrong.

People don't want to take that chance - and the mould is allowed to eat that food, not the huming beans. You could mainly still eat the food, the flavour is "off-putting".

NOW those of us with edificated palates are quite used to the flavors that penicillin moulds can give to cheese. If you have "cheese moulds" you could get them to grow on anything coming from a dairy - with the result that you have something that tastes of "blue cheese", as opposed to generally "mouldy".

Don't let that tiny fungal organism tell you what to do because it can influence your odoriforous sensibilities ...