That butter knife is an inspired design. How elegant.
I can imagine a pair of salad servers of similar design.
I carved 70 spoons and 30 forks, all in birch, for sale.
Preheat the oven to no more than 325F.
Slather the wooden utensils with the vegetable oil of your choice.
On a cake rack, over a sheet pan, into the oven for 3 minutes and 30 seconds by the clock.
Yes, there is a risk of the wood cracking. Never happened with mine.
Out of the oven, you will see little bubbles in the oily surface.
This is evidence of Charles's Law, a fact of gas physics, nothing more.
The heat made the wood air expand. Upon cooling, the remaining wood air contracts and pulls the oil into the wood,
far further than a simple soak can do. Paint on more oil as it cools = cannot possibly do any harm.
Now you have an utensil, oil-finished, which cannot have the finish washed off even in boiling soup.
You must reheat to more than 325F to get the oil to move.