Compound butter – it’s a ridiculously cheffy way to say something super simple. Mixing delicious ingredients into a butter makes it a flavoured butter – why we need to call it a compound butter I don’t know but that doesn’t stop it being a fantastic tool for any cook. I’ll delve into some of the science in a little bit but suffice it to say that there’s nothing quite like a compound butter for spreading rich, savoury flavour throughout a dish. Often you’ll use them to finish a risotto or maybe you’ll stir some jerk spiced butter into an apple caramel and pork sauce but compound butters also make brilliant toppings for roasted fish, in particular meaty fish like monkfish. Dense white fish, like monkfish, can stand up to hearty robust flavours like a butter enriched with umami bomb flavours like parmesan cheese and anchovies with chives adding a floral note and roasted hazelnuts for texture and oomph. Not only that, but it protects the monkfish like a little blanket stopping it from drying out in the oven. What you’re left with looks like it belongs in a fancy restaurant, but genuinely cooks in no time at all. It’s a little bit like one of my favourite fish dishes, herb crusted cod, but more luxurious and intense.
So why do compound butters work so well? One of the reasons is down to how flavour molecules work. Flavour molecules are often inherently volatile, which creates the aromas that our noses pick up and turn into flavour. Remember most of the flavour of something actually comes from the smell not the taste. Some flavour molecules dissolve in water and some don’t. Some dissolve in fats and some don’t. That’s called being a water soluble or fat soluble flavour molecule. For example, flavour molecules from carrots dissolve in water so boiled carrots are blander and less carrotty than carrots cooked in butter because the flavour leaches into the water. In addition, adding heat causes molecules to evaporate, effectively making them more volatile and more likely to either dissipate (think cooking off alcohol) or to be absorbed. This is why when making curries, they say to bloom the spices in oil. Effectively you force some of the volatile spice compounds which are fat soluble to dissolve into the oil and the water soluble compounds get captured when you then add the cooking liquid so you extract maximal flavour. Butter is about 80% fat (the exact proportions vary quite a lot from brand to brand) and about 18% water. That means that as it melts it captures and transfers both fat soluble and water soluble flavour compounds, especially when combined with something like fish which gives off a lot of water itself. On top of that the remaining 2% of butter is basically milk solids which accelerate browning and flavour development.
You can modify this recipe to work with whatever kind of compound butter you like. The recipe below is more of a template, covering my favourite big hitters of flavour and texture. It’s designed to be intensely savoury, with as much umami as possible, which works perfectly with really meaty fish like monkfish, hake or even cod. However, you could just as easily spice it up with some cayenne pepper or a little chilli. You could go Jamaican and throw in some jerk spices or blend in garlic and parsley for a Mediterranean vibe. However, the one thing I would suggest is that you try and think a little about adding texture. It could be roasted nuts like the recipe below or perhaps some toasted breadcrumbs sprinkled on top after it’s done cooking. I loved serving it with pickled shiitake mushrooms, pavé potatoes and an intense carrot purée but it can be tarted up or played down as much as you like. Trust me though, whatever your take, this one’s a winner.
I hope you like this recipe as much as I do – if you do then please let me know in the comments or if you want to receive an update on new recipes and tips and tricks then sign up for the newsletter. It’s just at the top of the page on the right if you’re on a desktop and at the bottom if you’re on a phone.
Hazelnut and parmesan crusted monkfish
Ingredients: (serves four – with a lot of flavoured butter left over)
- 1 whole monkfish tail, filleted and cut into four pieces
- 250g butter (you won’t use all of this but it keeps a long time)
- 1 bunch chives, finely chopped
- 100g roasted hazelnuts, chopped
- 8 preserved anchovy fillets, finely chopped
- 100g parmesan cheese, finely grated on a microplane
- A dash of Worcestershire sauce
- Black pepper
- Cube the butter and add to a food processor, pulse until softened. Add the anchovies, some good twists of black pepper, the Worcestershire sauce and chives and blend until fully incorporated, you may need to scrape the sides down and continue pulsing. Add the parmesan and pulse to combine. Finally, add the hazelnuts and pulse to combine.
- Chill the butter in the fridge until firm – ideally in a thin layer covered by clingfilm. I find a greaseproof paper lined roasting tray is perfect. The thin layer makes it easier to cut and place on top of the fish.
- Cut rectangles of the thin flavoured butter and lay over the monkfish pieces, entirely encasing. Place on a silicone mat lined baking tray and reserve in the fridge until ready to cook.
- Preheat the oven to 190 Celsius. Cook the monkfish for 10-12 minutes and serve immediately.
TimedEating Tips and Tricks for cooking ahead
- The compound butter keeps well in the fridge for around a month. I always make with a full pack of butter and store for future uses. If making in advance, you may want to store in a round wrapped in clingfilm. You can slice the butter and then roll it to the desired thickness.
- The monkfish can be covered in the butter a few hours before cooking up to one day before. Fish can’t be stored very long without freezing so any more than a day is pushing it.
- The butter freezes very well. Simply thaw in the fridge overnight.
- You can freeze the monkfish with the butter on top but I prefer to freeze both separately. If freezing together, thaw in the fridge overnight and cook as normal.
- If making the carrot purée it can be made a week in advance and the pavé potatoes can be made a few days in advance and crisped to order.