Cook the bacon and set it on a paper towel lined plate to cool. Set aside.
Turn on the pressure cooker to the sauté setting. Add the butter and olive oil to the pot. When the butter starts to melt, add the onion, celery, and bay leaf. Cook, stirring occasionally, until onion starts to turn translucent around the edges.
Add the garlic and carrots. Let cook about 30 seconds, stirring frequently.
Add the thyme, oregano, salt, and pepper.
Add the potatoes and chicken broth.
Add the ham and stir.
Close the lid and set the steam release knob to the Sealing position.
Press the Pressure Cook/Manual button or dial, then the +/- button or dial to select 5 minutes. High Pressure. The pot will take several minutes to come to pressure.
When the cook cycle has finished, turn off the pot and let it sit undisturbed for 10 minutes (10 minute natural release). Then turn the steam release knob to the Venting position to release the remaining steam/pressure.
When the pin in the lid drops back down, open the lid.
Add the corn and chopped bacon.
Use a potato masher to mash up the soup (Only the potatoes and some of the carrots will get mashed).
Pour in the milk.
In a 2-cup glass measuring cup or a bowl, mix together the heavy cream and flour. Then add a scoop of the hot broth and mix it in. Then turn on the sauté setting and stir the flour mixture into the pot, stirring until chowder is thick.
When the chowder has thickened, turn off the pot, stir the chowder again.
Garnish as desired (more bacon, green onion, cheese, etc.) and serve.