I find white bread, and even some commercial wholemeal, gets into my system really quickly and sends my blood sugars soaring upwards, before the insulin kicks in and brings them down again.
So, if I'm going to eat bead, I either Bolus about half an hour upfront with my insulin, or have some protein, ie scrambled egg on one slice of toast, (not just two slices of toast and butter,) or eat Burgen bread which releases more slowly.
Also, I'll only have one slice at a time. If I really want two slices and I've got the time (if I'm having a leisurely Sunday breakfast with the papers, for example) I'll do all my insulin up front, have one slice, leave it an hour, then have the other slice.