First, peel the onion & garlic. Finely dice the onion & grate the garlic, keeping them separate.
Next, set a large saucepan over a medium heat then add in the vegetable oil & butter. Once melted, add in the diced onion & a pinch of salt then cook, stirring frequently until soft & translucent. This will take 5-10 minutes.
Once the onion is cooked, stir in the grated garlic, cook for another 30 seconds then add in the sweetcorn & stir to combine.
Add the flour into the pan, stirring to coat the sweetcorn then pour in the milk. Turn the heat down to medium-low then cook for 10-15 minutes until thick, stirring regularly.The sauce should be thick enough to coat the back of a spoon. Once thick, add in the grated parmesan & Dijon mustard, stirring to melt the cheese.
Next, transfer half of the creamed corn into a jug blender (or food processor) then blend to make a coarse puree. Stir this back into the pan of corn along with the chopped chives. Season to taste with more salt & pepper as needed then serve.