Combine garlic powder, onion powder, and chili powder in a small bowl and stir to combine. Rub spice mixture into each butterflied chicken breast and season with salt and black pepper, to taste. Set aside.
Select the “Sauté” function on the Instant Pot® and add one tablespoon olive oil once hot. Add seasoned chicken breasts and brown on each side, approximately 2-3 minutes per side. (Work in batches, if necessary, adding more olive oil as necessary). Transfer chicken to a plate and set aside.
Add remaining olive oil to Instant Pot®, along with sliced Portobello mushrooms. Season with salt and black pepper, to taste. Cook, stirring occasionally, until mushrooms develop a nice golden brown color, approximately 4-5 minutes.
Pour in chicken broth and gently deglaze the bottom of the pot, scraping up any brown bits from the bottom with a wooden spoon in the process.
Turn unit off and return chicken to the pot. Add lid and lock into place. Position the vent to “Sealing” and set the “Manual” setting to 3 minutes.
When cook time is complete, allow pressure to release naturally for 5 minutes, then manually release any remaining pressure.
To prevent curdling, temper the heavy cream by adding a small amount of the hot cooking liquid to it before stirring it directly into the pot. Stir to combine.
Serve immediately with some of the creamy sauce spooned over the chicken and mushrooms. Enjoy!