1. b3 is the Nimzowitsch-Larsen Attack and Opening Explorer (the database here) calls 1. b3 e5 2. g3 the "Modern Variation" and puts winning percentages at exactly equal should black plays the natural 2...d5.
I mean, it's got to be a playable opening. But, on the other hand, it's my belief that White really isn't utilizing the first move advantage properly if he/she is letting black occupy the center with two pawns in the first two moves.
@Lent_Barsen First thanks for your answer. But still, those are consecutive moves. As I remember it was a one move/two pawns at the same time which offers more advantage no ?
I see that you evaluated winning percentages : do you have a link ? Or is it just by experience?
years ago when I played it was possible to open moving pawn b2 and g2 one case at the same time.
That question was already asked online here:
https://chess.stackexchange.com/questions/14181/moving-two-pieces-together
The answer is that there is no such rule in chess that allows moving two units at the same time, although there exist some homemade rules that some people have used that are similar. I've never even heard of such a rule, the (basic) rules of chess were standardized about 200 years ago...
https://en.wikipedia.org/wiki/Rules_of_chess
...and I used to peruse archives of the oldest known chess games, and I never even heard such a thing mentioned or notated there, so it must be some obscure homemade rule. I don't know how such a move could even be notated in modern notation. Maybe "1. b2 and g2"?
Actually, there is a rule in chess involving moving two units at the same time, just not THOSE TWO.
It's called castling!
Many thanks for your detailed answer. This rule was given to me by the old priest who taught me how to play more than 50 years ago in an old and lost countryside.. So yes, I guess it was "some obscure homemade rule". 
Thanks again sensei !
Many thanks for your detailed answer. This rule was given to me by the old priest who taught me how to play more than 50 years ago in an old and lost countryside.. So yes, I guess it was "some obscure homemade rule".
Thanks again sensei !
well not homemade
i see other people use it too but yes its not allowed (unless you allow it lol)
There was such rule before standardizing the game.
In "A History of Chess" by Murray, page 852, there's written
"Wielius knows nothing of castling, and nothing of the later habit of opening the game with two simultaneous moves."
"There is a number of smaller German treatises on chess of the eighteenth
century, many the work of Jews, which reveal the gradual adoption of the
French rules of play, and the relegation of the special German features to that
variety of the game in which the players each began by moving two men on
their first moves, of which I have given an account, pp. 389-91."
"We possess most evidence for the spread of the first peculiarity—the
commencement of the game with two or more moves. That this is the case
is undoubtedly due to the fact that the rule represents the most conspicuous
departure from the ordinary European rules.
The earliest allusion that I have found occurs in the Traitte de Lausanne
(Traitte du leu royal des Echets, par B.A.D.R.G.S., Lausanne, n. d., but
c. 1675), where the author's 20th rule (p. 14) runs :
II n'est point permis pour le premier coup que Ton joue de pousser deux pions à
la fois."
Double fiancetto is a cool idea, generally it's a good way of avoiding theory and leads to fun whole-board positions... in certain lines against the Reti I'm playing a double fiancetto... it can also be good against Bird's opening in some cases. Really you just need time to pull it off... I hadn't thought of playing it as white in the nimzo larsen though... but you'll have an extra tempo, seems like it should work. But there's really no reason not to at least play b3 > Bb2 before g3 in your scenario. That way you may prevent e4, and you remain a little flexible. But even more realistically I'd mix in a few more developing moves before doing the second fiancetto. That makes it much more viable... something like this isn't too bad -
Hi, I'm an old guy so please bear with me: years ago when I played it was possible to open moving pawn b2 and g2 one case at the same time. Is it still possible? What is the name of that move? How could one achieve this in chess.com application? And how is it rated as an opening move ?
Thank you.