Can I charge my iPhone 15 Pro with my MacBook Pro 106w charger?

Charge and connect with the USB-C connector on your iPhone 15 - Apple Support

According to this, you can "fast-charge" an iPhone 15 with a charger that offers 20W or more of power.

Here's the highest-wattage power brick that Apple sells right now:

140W USB-C Power Adapter - Apple

The Compatibility section of the description says that it's compatible with all iPhone 15 series models. If Apple had a 240W adapter, I'd expect the Compatibility description to say the same thing.

IIRC, all USB-C cables are supposed to be able to carry up to 15W of traditional USB power (3A @ 5V). For USB-C Power Delivery, the voltage is negotiated between the devices, leading to negotiated power delivery of up to 240W (5A @ 48V). An iPhone 15 series phone would presumably negotiate for lower voltages, and/or limit current draw, so as to keep the amount of power flowing into the phone well below 140W or 240W. I'm thinking that if Apple says 20W is enough for fast charging, the phone probably won't draw much more than that.

It won't hurt to use the 106 Watt power adapter, but it won't help either, since it will not charge the phone any faster than a 25-30 Watt adapter.

Most users do not realize that the "charger" is actually in the phone. It automatically controls the voltage flowing into the phone.

Please read again that......

"It will not hurt......".....and....."...... it will not charge the phone any faster than a 25-30 Watt adapter."