Normally, for a pie say:
Fore-Blessing
Fore-blessing of borei minei mezonot, even if it contains less than 1.3 fl. oz. (39 ml, or 1/6 cup) of flour. 
After-Blessing
To say the after-blessing, al ha'michya, you must eat a total volume of at least 1.3 fl. oz.--even if the flour was a minority of the ingredients. 
            However, if you prefer the filling to the crust (if you would not eat the crust by itself), say the appropriate fore-blessing over the filling, such as:

• She'hakol (after-blessing: borei nefashot), or
• Borei pri ha'eitz (after-blessing if on more than 1.3 fl. oz. of the Five Special Fruits--figs, dates, grapes, or pomegranates:  al ha'eitz.